[Unclenick]

Kroil works. PB Blaster is perhaps the best at softening rust, though it smells bad. Gunzilla will also loosen rust, but is slower to penetrate than Kroil. Whatever you use, you will want to displace it with gun oil or a rust inhibiting oil, like Birchwood Casey Sheath, or LPS-2 afterward.

Keep the surface wet with your penetrant of choice for a couple of days before you start removing rust. That will give it plenty of time to find its way under the deepest pits. Use a nylon brush or an old toothbrush to get the weakest rust loose first. Note that steel that rubs off the steel wool will rust if you don't remove it. That just takes more penetrating oil and a rag. Actually, I find the industrial strength brown paper towels do the best job of rubbing and buffing for that. You could also use a soft abrasive polish like Iosso Gunbrite or MAAS or Flitz to go after the steel and the last traces of rust.