I have a bodyshop and the only way to get rid of those water spots is by machine buffing and polishing. Color sanding is not required. Hand buffing won't do it because you really need the speed of a buffer for the compound to do its work. Buffing is tricky, since one slip and there goes your paint, it is best left for someone that has that experience. Must bodyshops would charge a very nominal fee, since it doesn't take that long, and builds customer base. You would be surprised what a $20 bill can buy! Michael, Hollister CA