Personally I found kroil and 000 steel wool to work well, on my 22 rifle I have sitting out in the open on my rack I found some rust spots so I applied the kroil (penetrating oil) let it sit for a few minutes then scrubbed it with the steel wool and it looks like new plus it didn't even ruin the bluing. After that i just treated it with the recommended 3 coats of g96 and no rust yet.