Duelmex's Guide to Flawless as Possible Shiny Mews (or any Method 1 Pokemon in Emerald)
Requirements:
Knowledge of Emerald RNG and emulators
A Lua script that displays initial seed, frame, TID/SID, and IV spread if you do the actual RNG on emulator
Gen 3 Event Tool and Mystery Gift Tool (for injection of event, not necessary if you're not going for Mew)
2 GBAs with either a link cable or wireless adapters
2 Emeralds (at least one Japanese if Mew is your target)
RNG Reporter/PokeFinder(I use both)
Microsoft Excel/Google Sheets
Emulator with Lua and RAM Watch capabilities(I use VBA RR)
R4 card with GBA Backup (for transferring saves between emu and cart)

Steps:
1. Pick the spread I want, take note of the PID of the frame
2.  On emulator, start a new game, make a save state when you're about to confirm your name (this is when TID is determined), use RAM watch to see what TID you get when you press select and then return to the save state until you find a cool TID
3. Pause the emu, calculate what SID I need using this: https://www.smogon.com/ingame/rng/deducing_secret_id Then RNG the SID using this process: https://www.reddit.com/r/pokemonrng/comments/245ub2/gen_3_emerald_emulator_rng_tidsid_combo/
4. I have my TID/SID combo (you can confirm this with a lua script that shows TID/SID) now I'm going to play the game until I can trade with another game. Save into a .sav file and go into cartridge.
5. Trade my starter to my (beaten) other Emerald game. I then use the cloning glitch to get a ton of rare candies to level up my starter. I then trade the starter back along with some HM slaves so I don't have to worry about HMs. Backup into your .sav file
6. Beat the game. The fastest way to do this is on emulator, but you could do it on cart if you want. You need to get to the Battle Frontier and get your Frontier Pass. This is important because you need to be able to save Battle Videos to get to the extraordinarily far frames that you probably want.
7. This is a fairly technical step. You're going to use RNGReporter's "PID to IVs" function found in the Gen 3 Tools tab. Paste the PID you noted in step 1 into the tool. Look for the spread you're going for and take note of the seed. Now go into the "Researcher" tab of either PokeFinder or RNGReporter (I use PokeFinder for this). Select the type of RNG you're doing as LCRNG[R] (not LCRNG!!!!). In Max Results input the amount of frames you're willing to wait (I usually do 10 million). Paste in your seed and click Generate. This will give you a table of values. In "Search Seed(Hex)" type 0 and select 16-Bit High. Open up an Excel Speadsheet and set a column to be text only, set the neighboring column to convert hexadecimal to decimal (HEX2DEC function in Excel). Back in the Researcher table you're going to hit Search. It will highlight on a 0000 cell, the value we need is directly to the right. Paste that value into Excel to be converted into decimal. Press next on Researcher and repeat. Get a list of as many of these as you feel like, I do about a 100. The more you do, the faster the next step will be.
8. You now have a spreadsheet full of values that have been converted from hex. The reason to get these values is that they all are starting seeds that are fairly close to your very far away goal. You may have heard the initial seed in Emerald is always 0. There is one exception to this: a brand new save. The initial seed of a brand new save is equal to the TID in hex. So if you were to get one of these TIDs, you could hit your frame much faster. So that's what we're going to do. i'll divide this step into substeps with the final goal being to get the goal frame very fast:
	a. Take your two GBAs and Emeralds. We'll label the Emerald we're going to start the new game in as Game A. We'll label the Emerald we're doing the RNG in as Game B.
	b. If using a link cable, make sure Game A is the side that will be Player 1. This game absolutely must be Player 1.
	c. Start a new game in Game A. When the truck stops in the beginning of the game, check your trainer card. IF the TID isn't in your list of converted values, reset the game and repeat.
	d. If it is in your list, congrats! You're almost done. Play the game until you can connect to Game B.
	e. You're going to have a battle between the two games, after your Game B wins easily, save the Battle Video.
9. You should now have a Battle Video with a seed that is close to your target frame. To see how close, simply open RNGReporter and make the TID of Game A(in hex) your starting seed. At this point, backup the save and go back into your emu. Run your Lua script and head over to the Battle Factory. Play and quickly exit your battle video. Your Lua script should give you an initial seed to type into RNGReporter. You now simply use the Battle Video method to get a Battle Video that is really close to your target frame. If you're unfamiliar with the Battle Video method, here's a good tutorial: https://www.youtube.com/watch?v=HlhM6BTDXvc&list=PL4o9bTT3px_h08zUFb3oChEFku_jG6zyt
10. Now that you have a close Battle Video, you're just going to inject any necessary event items you may need, and RNG your Pokemon in either cart or emu! Hope this guide helps, I know it's extremely long and confusing, but this is what it takes to get the best spreads in Emerald to be shiny.