0000 steel wool and oil work just fine. I like to use the steel wool dry,then put the gun oil on. Like Gil said.Be gentle. If the rust is real deep you can use Navel Gel,but it likes to take the bluing with it.It's better to get all the rust out and re blue. If it is pitted you can use sandpaper.Start with 320grit then 600,then 1200,then steel wool it. Just make sure you oil it after your done.