your plastic hair comb is not a good conductor but it can hold a charge. rubber is also a terrible conductor, but it can also hold a charge(think of a balloon). shop i called up to quote my rims said, they could do most plastics. But i just figured i answer number 2 first before i answer number 1. guess im wired backwards?
Question was mostly asked out of convenience, so i can give my wheels and tank to 1 shop to have them do it all instead of splitting it up.
Ive also seen an application where the powder is sprayed in one nozzle and a torch is ignited to heat up the powder and then finnally melt it once it contacts the surface your spraying on. But i looked a bit deeper into it and no matter how i look at it your spitting way to much heat onto that surface.