If you have two Pokemon that have the same EV training build, equip power item that adds 8 Attack to PKMN #1, and equip power item that adds 8 speed to PKMN #2. If you switch power items after EV training in attack or speed in an SOS battle knocking out 14 mons, and switch to the next EV training. You'll max out 4 EV's only Knocking out 28 Pokemon!