I actually use this product I bought at Blue Ridge, I think it's called Aseptox... it actually acts as a cleaner and no-rinse sanitizer. I pour a gallon of warm water in the BB, add a tbsp of Aseptox, shake, and then put a cork in the opening. Then, I turn it upside down in the sink, and leave it for 20 minutes or so so that the solution is in contact with the harder-to-clean area where the krausen was. I then drain most of it out, throw in a dishcloth, and roll it around to get the stains off. Usually works very well.
Blue Ridge use to sell them, but then they moved to something the owner claims is "better", and is about twice the price... which is ridiculous, I think. You can buy them at Noble Grape for low-20s, I believe.