I've been using Diablo for the past year as I wanted something that would be "safe" on my rims. Okay, I'm still looking for a better wheel cleaner for my BMW wheels. Diablo is definately not spray on and wash off, although a little aggitation normally loosens up most everything to wash off as long as I wash the rims weekly. If I can't wash my wife's BMW's rims every week or two, the Diablo just won't take everything off easily, even when using a wheel sealant. I end up having to use other things to get baked on "stuff" off the rims.
It also definately doesn't cut the black bloom and wheel dust from the tire rubber. I found that Opt Power Clean is much more effective on the rubber. P21 and Sonax will probably be the next one to try, even if the OP didn't want to spend that kind of money.