We mostly used foam rubber sanding blocks over the surface of the car, sanding with 800-grit wet sandpaper until the clearcoat was completely smooth, if not gone completely. Basically, when we started seeing red paint rinsing off the surface, rather than the milky white clearcoat, we stopped sanding. We did break through the red basecoat in a few spots, but that was OK because we planned to spray the car with one more coat of base anyway. Still, this is a good reason why you should buy a little more paint than needed to paint the car. It’s good to have extra for touch-ups or bigger fixes like this.