I have powder coated all my off road racing ch***is and they held up very well extreme harsh conditions that we but them thru racing the Baja 1000. However on my new ch***is for my 30 build I personally painted it with Dupont Imron Elite Top Coat. Everyone cannot believe the look as no orange peel at all, in fact most say "so who powder coated it"
Yep , I sanded it with 320 and painted it . No problem. I did'nt know that there was a powder primer until I was telling the PC guy that I wanted to paint over his PC . He was the one that suggested the epoxy PC .
I PC w epoxy all the time at work (big pipe fittings) Just remember epoxy oxidizes (even in the shade) so put something over it.