I bought my Sil high-mounts used and the left can had a pretty good rash, maybe 1/4 inch deep and roughly 2-3 inches long. I got such a good price I bought them anyway, as I knew I was going to paint them.
Here's what I did: Wet sand them to give texture. Fill in the dent/ding/rash with a nice spot of auto body filler. Reshape. Sand. Paint.
After painting (flat black, natch), they look about 95% perfect. Took a couple hours work.