Pardon my ignorance,
The powder coat is not harder than paint?
If so why use it?
Personally, I sand blast and paint my own steel rims and never any troubles.
Even after several changes.
Also no trouble with aluminum rims.
I take all my wheels to the local garage.
He has been in business since the '70's.
Equipment is as old.
I do make sure Fran does the werk and not one of the kids.
He gets a tip, and all is in cash so no invoice.