I'd let it soak in MS before with no ill effects, but never for more than 20-24 hours, and never MS mixed with Hoppes 9. I'm not sure if the MS/H9 combo, or the fact that I scrubbed it good and left it for a couple days.
A little part that was left sticking out had the finish left on it, so I let that part soak on the bottom overnight and it took the rest off. There were a couple of little spots left but steel wool took them right off.
eta:
To answer your question for ammo, Stingers are the best but they are also the most expensive. If you really want a treat, shoot the Stingers after dark, if you can. All I really shoot through it anymore is the Federal 550 bulk packs from Walmart. $9.88 for 550 rounds is pretty good.
It shoots great, but MAKE SURE as well as the gun, you clean the magazines too. I was having all kinds of problems, and cursing the gun, but most of my problems were from the dirty magazines jamming up. I cleaned them up and it works GREAT now.
I'm just waiting on my suppressor right now