Hot soapy water, but I've gotten careful to not clean too much. The thing stays covered in Ballistol and there is bore butter over ever ball that is shot so I treat it like a frying pan that is seasoned. The big issue for me is avoiding corrosion around the nipples, I will scrub that area to death, mop the cylinders with ballistol and then snap a few caps on them to clean everything out. I've left it loaded for a year with no rust issues.
You need to work on your rate of fire.
The first time I had mine to the range I ran through 2 100ct boxes of balls. I had forgotten my bore butter so I stopped at an auto parts place and bought some lithium grease. Worked great, by the end of the day everything, me, my range bag, attendant AR-15, the entire area of the range was coated with grease and soot.
