Using the 20XX Hack Pack

The 20XX Hack Pack should just be renamed the No Johns Hack Pack. There is a ridiculous amount of mileage you can get out of this as a player provided you have the minimum dedication to learn how to execute the maneuvers you have trouble against, and the patience to test extensively if necessary. The post will contain the preliminary stuff and the comment following will contain the methodology. I think the post is essential to understanding what you're practicing, but if you're just looking for what I've been doing recently, then go ahead and just skip this. But maybe you should skim this post, for real.
An immediate and very useful application is if (like me) you are struggling against Falco shield pressure. Falco shield pressure is crazy because of the beefiness of his aerial and shine, as well as the option to grab out of shine (and double shine to cover rolls). Furthermore not all of his created scenarios are reactable, and worse yet he has many ways to condition you towards one reaction or another. Oh well! That's just Fighting Games 101 -- there will be highly non-interactive, disadvantageous situations; so long as you wanna play, you gotta find a way around them. For the reactable situations, you react; for the non-reactable situations, you find ways to recognize when they get started or how to defend when they're started; and you find ways to give yourself a margin of error.
Anyways, let's get all the preliminary stuff out of the way so I can explain how to practice. Assume that Falco has already gotten past the neutral stage and has successfully gotten you to decide to block (also assume no powershield). From here, you can break down the pressure into before/during/after (these terms used in context of Falco's timeline):
"Before" stage: before he interacts with your block directly, he will choose to shine or come in with aerial (he can do jumping shine but this is only a relevant options with platforms, and I'm only discussing a no platform case in this mini-essay). Generally speaking, since Falco is slow on the ground, there are very few occasions where he can running shine you without incurring a large amount of risk. So if he shines, it will be from a laser. On the other hand, Falco's aerials are performed while moving and beat out a lot of moves due to their startup, so he doesn't necessarily have to have a laser out for those options.
"During" stage, shine: So if Falco decides to use shine, it will either hit spaced (the edge of the shine) or deep (his body meets your shield). Discussing timing variations in shine go a bit beyond the scope of this post and I also don't have a great understanding of it, but the gist of my current thoughts are that the shine itself isn't performed from a jump so there's only one "timing" of shine, and any variation in the timing of the move is from you, not from Falco.
"During" stage, aerial: Falco decides to perform an aerial. GENERALLY SPEAKING, Falco has set up/decided before hand the side he lands on and spacing(s) and timing(s) of his dair or nair, as well as the state of movement. Plural, because some lead ins are set up such that Falco can semi-react to your position and choose timing/spacing from there.
There are two sides: same side, cross-up.
There are three ranges for nair: max(anywhere from foot to knee)
spaced (hits at knee)
deep (hits with body).
There are three ranges for dair: max (toes to mid shin)
spaced (shin to stomach)
deep (hits with whole body).
There are three heights for each aerial: high, mid, low on block.
There are three "states of movement" during each aerial: toward, retreating, stationary. The states of movement are included here as an afterthought because they mostly affect the spacing and timing of the moves, but they'll get more love in just a second.
"After" stage, shine: From this shine he can either do an immediate shine (i.e doubleshine), jump shine (which will then be double jumped to safety unless the Falco is suicidal), aerial, or grab. Or laser, but unless your character is bad or you're bad you should be able to reliably react to him choosing that option.
"After" stage, aerial: From the aerial he will either cancel into shine, grab you, move (wavedash or dash out, neutral SH/FH), or aerial again.
The point at which Falco decides to perform another aggressive maneuver from your shield is when the "cycle" starts again. You may or may not be able to counter him directly at that point depending on the action chosen (a nuance I won't really get into because I'm learning about it myself). The aerials performed from the "after" stage are often confusing because they can have a different "state of movement" from Falco's initial movement/previous movement.
Whew! That's a mind-boggling amount of stuff to consider. So how do I even begin to tackle this?
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Using your 20XX hack pack, go to Debug Menu -> Results Test. Toggle RandMusic to 0 (seriously, fuck that shit), and toggle Colors/No L-Cancel flash so that way you can see shieldstun/execution errors.

Then, go to VS mode. Select Falco, set P2 on human as your character (for me it's Sheik). Go to FD to start with; ~80% of Falco pressure can be learned about without platforms, the other 20% I'm still figuring out how to learn with the hack pack heh. Toggle infinite shield, put P2 (your character) in the middle of the stage (just walk them there).

Then, decide what you want to test (shine, aerial). Move Falco to the relevant range, save state.

It's simple enough from here. Thoroughly test each option you wish to understand, using load state to speed stuff up. The hack pack can be toggled for P2 to perform various actions OOS (grab, [forward] nair, cstick buffer), which is really really useful. For me, I don't know anything about Falco, so I've begun mapping out his "During" stuff out on a word processor like this. After each spacing category I list the timing; after each timing category I list whether or not nair/grab OOS will work (and whether or not I think WD OOS or roll could be used to avoid), along with considerations of movement state if they change the situation(s) at all:

"Move
Side

Spacing (Max, Spaced, Deep) - Height (High on block/mid on block/low on block) - Movement state (stationary, retreating, towards)

Assume Sheik is facing forward. Backwards in all these scenarios is different but most of the time you will have to hold that shit if he’s hitting the back of your shield.
All nair OOS here are tested with 20XX dummy, meaning that stationary nair is the only permutation possible. Therefore, this guide is not comprehensive."

From here I plan on studying "before" and "after" stuff, though not all of that is Hack Pack related.

After you understand the individual options, you can start linking them together. For example, if Falco deep shines, and you don't anticipate him to double shine, then (without shield DI factored in) he is absolutely restricted from x options, and can perform y options. It's probably really laborious to string ALL of the possible permutations together, so at this point I would watch videos and dissect common blockstrings/specific block strings you have trouble with. Remember that you need to split up his maneuvers into their components to understand how you want to respond to them.

Additionally, the 20XX CPU will do the frame perfect stuff but that's not feasible to perform 24/7 in real life. So when you're training for this you will want to consider how you might be conditioned one way or another, or how much leeway you have. If you're more visual and not very mathy and don't want to use the shieldstun calculators (just google), you can just set P2 to hold shield and look at where the pink flash (i.e. shieldstun) ends.
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This is but one example of how to apply your 20XX hack pack in an exciting fashion. If we're talking vs. Falco, you can also start honing your powershields vs. lasers w Corneria and toggle standing SHL option (thanks Kevin Nanney), or start learning how to counter lasers with moves/movement. Vs. other characters, you can imitate movement patterns of characters you want to practice against (ex: Marth, Falcon) and get a clear understanding of how their dash zones work. Using hitbox viewer, instead of looking at gifs online and using your imagination to put those gifs and movement together, you can get material for image training much more easily performing the given maneuver on your own system.

I'm sorry if I went on a bit long about training. I just want to see the Platinum Age really take hold in NC. There's a lot of people who want to play the game, and presumably want to get better. How large/persistent this fire is remains to be seen, but I think that the illustrating the potential of the No Johns Hack Pack is a great way to make people excited about learning the game/improving. If people are interested I can occasionally write more content in this vein (I'm still working on the TO primer tho :x so I want to finish that first)..as for this specific piece, I really just wanted to share my excitement about my training with the rest of the state.