what about EV lowering berries, you EV it up and at the end use one EV lowering berry. Would that work?
You cant give Evs to level 100 pokemons. To gain Evs in D/P you need to gain exp(excluding vitamins) that is why level 100 pokemon are a bit useless as they cant get more than 100 Evs in a single stat. You can use Ev Reducing berries even at level 100 if you are not talking about TRU regigigas anymore