I've found through trial and error, and boy were some of the errors DUZIES, Brake Cleaner is about the best stuff one can find for degreasing metals. Rather than using something that works "okay", use something that is actually designed for degreasing steel! I'm not talking about the Break Clean for gun cleaning. I'm talking the stuff in a can made for degreasing/cleaning the oil off disk rotors. Stuff is great for this purpose but be warned, I am NOT talking about regular gun cleaning practices here. Brake cleaners, most with the chlorine in them, will strip the finish right off ANY wood and will disintegrate a lot of plastics. It also takes the oil right out of the pores of steel, even stainless, so I am NOT recommending it for use as a regular cleaner. Just for this purpose of bluing or browning barrels.