Been powder coating at home for years now. Those wheels being aluminum would've benefited from prebaking. Aluminum is porus and tends to absorb grease, oil, and all kind of bad things. I typically prebake them for about 30 minutes at about 450 then cure them at 400.
That's one I did for my Bug. The orange on the edge is just paint overspray. I can't even begin to describe how ugly that wheel was when I started.