cbass68 - Any flat or semi gloss paint, powder coat, or plastic for that matter, will gloss a little if rubbed hard enough. It will eventually even itself back out with regular washes though.

I'm not exactly sure if you intend to have the flames glossy with the flat black background or flat flames as well. Either way, a painter is gonna want to shoot clear over the flames to seal it all in. If he uses gloss clear you've lost the flat black but he could use a flat clear... of course that would make the flames flat as well. BTW, painters can paint over powder coat with no problems. There's a custom painter here that airbrushes and pin stripes over my powder coat all the time.

 

I think the only thing not covered is just that when you paint tins you are doing body work to the tins making everyhting nice and smooth with powder coating if the metal is in bad shape you will see that..

 

Los11 is right, but there are metal body fillers designed to be powder coated. The down side to those fillers is they can't be used too thick. So, if you have a large dent you'd have to either fix it with a bondo type filler and paint or get a new piece. Another option to small imperfections is brass. Braze some brass into the area then file and sand... powder coats great!