This works best from 1-75. After 75, the damage is so small that it isnt worth the trouble.
Join a mini game. Once you are in app'd level up to the max cast, cast all of your buffs and despoil the foul. You can quit the mini game now if you want. Your buffs will not drop when you leave...even if you are killed.
You will have the damage bonus from despoil of your app level, not your actual level.