Find another paint shop.
Basically, powder coat is an extremely durable, heat-set plastic that's "sprayed" onto the substrate while the powder has a positive charge and the substrate has a negative charge (attracting the powder to the surface). Scuff it, prime it and paint it. However, not all powder coat jobs are equal. If the surface wasn't prepped proper, the powder was heavily piled on or the oven temp/duration was incorrect, adhesion may be compromised (that may be why your guy shied away from the job). A local powder coat shop can re-coat the piece, in just about any color, after they've stripped the piece (acid dip tank), hit it with a media blaster (giving it "tooth") and cleaned the surface with alcohol (a final cleaning and static neutralizer). Ask about a powder coater's prep. If they stumble with words, find another. Powder coat has been around for decades and an experienced metal finisher shouldn't have a problem explaining their process. I would expect a piece the size of a 5'er tailgate to run about 200-250 skins, for a quality job with a warranty. I'm guessing about the fee schedule, based on custom motorcycle parts. The guy I know, who's quality is top-shelve and reliable, is backed up for two months. At least, he's honest about having to wait, rather than blow smoke.
