>>15657936Basically:
-put parents in daycare
-get egg, reject from daycare guy
-save
-get another egg
-hatch
-determine who passed down what IVs
-reset game
-swap parents so that the passed down IVs are 31 (the inheritance stays the same even after a game reset and changing the parents)
-get egg
-hatch
-perfect IVs
It's sort of an "accelerated" process, the more parents with a different combination of IVs you have, the easier it is to very quickly get perfect Pokemon.
It's also pretty much the only way to reliably get a Pokemon with 31 in all IVs.