I've heard a lot of good things about the Dixcel rotary brush, so will have to buy one and see. Presently use a piece of wet denim and it's worked for a lot of bbls. I think the amount of rust due to the process {time, humidity} determines how severely the bbl has to be carded. After neutralizing w/ ammonia and rinsing, I use 0000 stl wool w/ Lube 1000 for a final, light rub down which "softens" the matte etching....Fred