Thankfully I've never had too many guns that had rust on them but when I did, I used 0000 steel wool and gun oil to remove it. Now all the conventional wisdom say not to use steel wool because the tiny fine particles left over from the wool will cause the metal to rust yet again. Thankfully I never had that problem as I always made sure to get all the fine particle off by soaking in a bowl of Hoppes 9 and using a toothbrush to get everything off, but the basic accepted method today is to use Bronze or Copper Wool and err on the side of caution. I can't really argue with that theory.