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Eh, I just use them like a normal avatar gets used. There are a few times where my avatars don't animate for some reason, though I usually just get a different sprite gif with the same character to solve the problem.
Stealthing it. 100% w/ no kills.
I slowly pick them all off one by one until there is no-one else there. Groups get fun and it involves stalking every single person 10+minutes each, but I feel that getting that no-kill achievement out of the way early is worth it...