I'm not sure why gun cleaners would be particuarly good for cleaning propellant residue unless you were working with NC based propellants. The solvents are a bit specific.
Ballistol, I don't know. I haven't used it for that purpose.
I prefer to clean cases while still hot, and an ammonia based cleaner tends to work. Don't soak and don't waste time! Soaking would damage the surface of the case. I'm not going to tell you this is completely safe for your case.
Use with a large nylon bristle brush and an electric drill. Sort of like a test tube cleaner on steroids. You can get the brushes at least up to sizes where you can just skip the brush and stick your arm in the case easily. Cut the loop handle off the end and chuck it up. Get caveman with it! Then when basically done can wrap paper shop towel or similar on outside of brush and run that through. There are probably better cleaners, but it works well enough for me. If one cleaner doesn't work well for some reason, clean it up, switch it out to something else.
Don't use chlorine based cleaners. That would probably pit your case in relatively short time.
Gerald