I would not wetsand anything on the car.

If you have stains on the paint, you need to do a chemical wash- much safer on the paint then taking it off.

Try Body Scrub from megirurs (sp?) use with some hard pressure, just might work- If you want do the whole car with it- look amazing ( but will take you a long time if done properly) also their ScratchX is nice to bring up the shine after.

Yes there is more exspensive and better stuff, but for a quick thing and easy to find... one of the better.