Once I accidentally spilled alot of the hot sealant and then accidentally drove into it with my truck. It covered my tire, and I thought I was going to have to buy a new tire.
I went out onto the highway, and drove (slowly at first) then gradually started going faster and faster. It was a very hot day, so that helped also. Eventually, the stuff heated itself up enough to where it just came off. You might want to try that, you probably won't have much luck trying to get it off with screwdrivers and such.