Does anyone know the best way to get paint off of rocks? We are doing some graffiti clean up at a climbing spot here in NV. We have no running water up there but we do have a gen. I am thinking about a flapper disc on a grinder. We have tried goof off, paint thinner, laquer thinner , just about every chemical and we cant get it all off. Does any body have any suggestions before we turn to angle grinders and flappy discs.