You can't just top it with clear and polish?
The insides of the rims look like sh#t!!!
you apparently have no idea what you're talking about.
once the powdercoat is stained, cracked, flaking...it CANNOT be fixed. if it's surface crap, clean it off and polish the wheels (NOT SOMETHING ABRASIVE, IT'S NOT METAL). like a wax.
If you cover clear with clear, it's still clear.