I use an Oxo wheel brush and plain Z7 washwater for general cleaning. If my wheels are especially dirty I'll use Eagle One Aluminum wash which does a real good job and is pH neutral according to the label.
If you're concerned about cleaning the backsides of your wheels give foam paint applicators a try. They're very soft and come in various sizes and are inexpensive. Umm...pay no mind to the rollers in the pic, it was the only image I could find.