Did this type of design Swirls; in school,years ago, we used a dowel 1/4", 3/8", or the size wanted , dipped in a small amount of oil,; dipped into the abrasive material;( grinding dust from the bench grinder,)or other abrasive material,Silica sand; from the hobby shop , a bit of oil wiped on the metal surface to be designed, worked quite well; but the trick was to get the swirls in a straight line, best to practice on a bit of scrap material first, OMHO..