How would I go about painting my opal finish rims to white and have a nice shiny gloss finish?

Powder coating them. Just slapping some high gloss paint will only fade the color. A good Powder coating job should run you around $200 for 4 rims. Thats what i was quoted, when i had an idea on doing that to some Z24 wheels.

anodizing depending on the metal and the finish...