Was using the truck to haul sand and morter and we mixed a load that was a little sloppy. When we poured the batch it splattered everywhere including on the paint of my truck. Obviously I didn't get it all off when it was still wet and now i have some small concrete spots on the truck. I have washed it 4 or 5 times, used bug and tar remover and even had it waxed... nothing seems to remove the concrete... any suggestions?