I got a lapidary belt from Kingsley North thats a 300 grit abrasive wheel that goes on a 6" expanding disk on an electric motor. A few seconds per pot makes the feet of all my pots velvety smooth. In addition, I burnish the foot with a silicon bone folder (for stationary) and sometimes never have to touch it with the lapidary belt. I use Bmix ^5 so the grog is not an obvious problem.