I repaired some curb rash on the outer rim of a 2-piece BBS Triton wheel on a Volvo. The rim appears to have a machined finish with a clear coat. The paint I used matches well enough that the repair is barely noticeable, but in the process of sanding the rim to prep it for clear coat, there developed dark spots on the surface of the rim. I have tried removing them with various grits of wet/dry paper and nylon pads but they don't come out and actually get larger. Is there something or some way to restore a uniform finish on the rim?