Wheel painting

A couple of questions regarding wheel painting. I've been offered a set of wheels for the exxy. They have been powdercoated in what I'm told is metallic silver. Unfortunately they look more like a flat grey undercoat. The surface finish is good it is just the lack of silver/metal in the colour.

Has any one had any experience with painting over powdercoat and what sort of surface preparation is required. I am told that paint won't stick to powdercoat. It is not really cost effective to have the wheels blasted. The powdercoat also hides a lot of the surface imperfections. Look forward to hearing people's experiences and views.

Regards
Peter