I've done it similar to Lumpy with 20 Volume Developer I get from the beauty supply store in gallon jugs. I mix one gallon developer with maybe eight gallons of hot water and a couple of scoops of oxyclean powder (I mix it in the hot water jug and shake to dissolve) all in a clear, plastic tub. You really need some clear, sunny days to get it going well. It also seems to work better for me in the warmer weather. It can take as little as 2-3 hours to be "done" with some strong sunshine on it. Be sure to flip it every so often to get some even UV coverage.