PlatinumSukamon (they have an inheret skill that increases XP gain, this stacks with more PlatinumPoops in the front party)
Each one has all of their held items be Tactician USBs (items that increase XP gain, they stack with each other and stack with the PlatinumPoops).
PlatinumNumemons are the mega versions that can hold an additional USB each.
You'll have to wear a neck brace after experiencing those XP gain speeds.
It's a weird as hell way to get XP but it gets results like no other. Only in a Digimon game.
Think of it like a microtransaction, but instead of "this much money/game credits per minute", think of it using your dignity/per minute as a currency.