Powdercoat will probably destroy the filler (unless you use lead or some other high-temp filler), and you can't really get flip/candy/pearlescent/proper metallic powdercoats either. I've read about companies that do pearlescent powdercoats but I've never seen them.
Get it painted properly, I say, by a specialist automotive/custom painter. House of Kolor ftw.
From the current projects page:
It's an Armourtex job - Ral 9005, with Emerald Illusion* finish, because I like Ponies and Unicorns.
^