I don't know a ton about stock wheels of cars. From my experience with motorcycle rims, it is a major pain in the back side. Sand off the clear coat with one grade of sand paper, sand down the ridges that the first sanding left with a less coarse paper, sand again with an even more fine piece of sand paper. If you want it perfect, sand yet again. Then you start to actually use a metal polish to bring out the shine. Like I said, my experience is with motorcycle rims. Automotive may be easier...but I am fairly sure there will still be a clear coat on the rims.