Hand over the Apricorns for the appropriate Ball you wish for; Kurt can only make one type of ball, but can produce more than one at once (limit to how many is yet to be determined).

Save in front of Kurt's house.

Turn your DS clock off and back on, set the time to 23:59, and load up the game immediately.

Let the day pass in-game (23:59-00:00).

Enter the house and receive your Poke Balls. Repeat as often as you like.