Don't use 500 grit paper, that is what you use to prep for paint. 1600 grit with lots of water will give you a almost polished finish that can be finished of with a good wax.
had a couple of rub marks on the 39 chevy i built, from my jeans, used 1600 and a claybar and fonal wax and you couldn't tell it had ever been marred.
