i suggest you take a pic of the worn anodizing before you attempt to remedy it. some rims (such as the Mavic Open Pro CD models) have splotchy coatings due to the tension on the rim from the spokes putting tension on the rims. those areas that are lighter are slightly raised compared to the rest of the brake track, causing the hard anodizing/ceramic coating to wear faster on those spots. the photo that
SJX426 is a great example of what happens over time.