That thing's dangerous, if you don't stop every couple of seconds the clay will fill up with contaminants and mar the crap out of your paint. You also can't tell if the lube has evaporated so you'll either waste clay lube or leave behind sticking clay. The worst part is that if you get a piece of actual grit in the clay you'll scratch the paint really badly, the kind of scratches that it's hard to get out with a rotary.