It's currently soaking. I did one soak, it did a little bit, so I'm soaking it again. Let's see how it turns out
Salt and vinegar cleans tarnished copper coins. May work on green oxidised coins. https://www.youtube.com/watch?v=H4N-iGvYrbM https://www.youtube.com/watch?v=g1rnlRk0x-k
Cloudy Ammonia is for silver. And, removing copper from the bore of your rifle! Its best to use it on 800+ silver Coke works very rapidly on copper. And is perhaps how most people cleaned there first coins as kids. The gentlest "quick way" is Tomato sauce. or even safer, soak them in olive oil.