After 35+ years of owning numerous antique firearms, I know that cleaning them can be a chore. I buy brass bristled toothbrushes at my local hardware store. They do not cause any harm to original finishes or real patina. For thick rust, I use a piece of brass stock and scrape the heavy residue off. I see on many forums where 0000 steel wool is recommended, but exercise caution. We should all exercise caution, regardless of our cleaning methods, but brass cleaning implements can be used vigorously without damaging existing finishes. Brass may leave streaks on the steel surface, but quickly disappear with Hoppes #9 and a rag. Bronze wool is also a wonderful tool for safe cleaning. Good luck!