I just did some rock chips touchups on my metallic black yesterday and the results were amazing. I purchased the factory touch up paint from BMW, lightly sanding the chips edge with 2000 grit sandpaper. Did several chip fills with the end of a toothpick that was dipped in the paint. Once the chip was slightly bubbled above the surrounding areas then I lightly wet sanded the bubble level with the surrounding area, and then hand polished the area to remove any scratches and the chips were about 80% perfect. I plan to do one more layer of paint and then sanding to make it perfect but for the first try I was floored with how easy and how good it looks. The defects are only visible now when you look at a hard angle from the side, then you can see the small recession where it needs a tiny bit more paint. Looking at it from above even with a powerful flashlight you cannot (and I am really stingy on what looks good) see where the chips were. When I showed my wife she couldn't see the remaining marks that I could see at an angle even when I pointed them out to here. Anyhow, the thought of using sandpaper is a little scary and seeing the scuff marks is even more so, until you polish and then see the great results.