A 1 step spray wax you might consider is PB's QW+. Light cleaners and decent durability, esp. for the little work needed to use it. Even works on moderate oxidation, if you were so inclined to try. Can leave to haze, or can buff it right off. (One additional benefit of QW+ is that it can be used in the sun, in case this makes a difference to you.)
OTC, you might consider Mothers FX Spray Wax. Can be used on a wet surface, and no haze time required. Reflections Spray Wax is thicker, but I haven't had any problems using it on a wet car. In fact, the water seems to help spread it further. However, this one needs to haze, so you may not save much time with this route compared to a traditional wax. Does look very nice, though.
One thing about spray waxes, that I've noticed, is that the "white" ones tend to leave little white specks all over the glass, nooks and crannies if you mist it onto the car. I've found spraying it onto the cloth works better.
As to the RainX, I don't see any great cost savings by not applying it with each wash & wax, as a bottle can do many windshields, and is relatively inexpensive. Now, if you were applying Aquapel each time, that could get costly.