I'm guessing you gu s dot know about the trick, but one of the fastest ways to get customs is to do Crazy Orders with equipment that gives you a home-run bat and a specific piece that heals you when you deal damage (not sure what the name is). Since you can KO at any percentage each match will only take a few seconds. I recommend choosing tickets who's prize matches the series of who ever you want to get customs for, but make a priority to go for matches with the least amount of opponents (don't do hoard, and be weary of Giants). Also, before you fight Crazy Hand, make sure you face a metal opponent and let them rack up damage. When you're satisfied, finish them off. This way you'll have a lot of damage on you which will convert into more health for the final match.
My explanation was kinda off, but just google it and you'll get a lot more info.
My explanation was kinda off, but just google it and you'll get a lot more info.