A "softer" material of rod shape carries abrasive while turned/rotated against a "harder" polished surface. So, a "rubber" rod works well as the "softer" material, adrill press is good for powering the rotation, and oil base abrasives do well as the "scratcher" material. The scratch circles must be overlapped in both directions. An X-Y table will make for very even spacing of the "swirls." Too fine an abrasive and the scratches are too small to see, too course and they don't look good. The level of polish also plays a role.
Cratex abrasive rods work reasonably well. There is considerable range of grit so you can experiment with the polish, metal hardness, and grit.
DDA
