My powdercoater only requires the frames to be bare of extra parts, and preferably with any stickers peeled off. An unmolested coat of paint is easier to media-blast off than paint and stripper residue. He does all the masking, and does so perfectly, no slop or overspray...he knows exactly what needs to be masked, he's done a lot of bikes.

Given all the different stories people are giving, OP needs to talk to his powdercoater first to see what he/she prefers to receive.