You guys are going to think I am nuts, but try crumpled up newspaper first. Many years ago (late 1972) I had an 870 Wingmaster that rusted almost overnight after a pretty wet duck hunt. I took about three full sheets of newsprint, crumpled them up and wrapped them around the barrel. I was amazed at the result; the rust came off and the bluing at least appeared to be unaffected.
Over 40 years later, that barrel still looks surprisingly good for its age...
Over 40 years later, that barrel still looks surprisingly good for its age...