I'll add to the list of good cleaners various brands of Brake Parts Cleaners (aerosol). I had to clean up a new shotgun that I got for the grandson and after spending a couple hours and a bunch of patches saturated with various gun cleaners such as Hoppe's #9, Shooters' Choice, Outers, etc., I was still pulling out dirty patches from that cosmoline-like grease they use on their barrels. When I showed it to the boy, he said Gramps had to do a little better.......!! So I purchased a can of brake parts cleaner, saturated a couple patches and swabbed the barrel out. Lickity-spit clean just like that! There are good gun scrubbers on the market (like Birchwood-Casey's), but this was alot cheaper at Wally-World auto-supplies dept. Just be careful where you spray the stuff, and keep it outdoors. Pretty flammible and toxic fumes too.
Jim