You raise a good point about air flow. It would probably work better to paint the wheels standing up, as opposed to laying flat on the floor (or whatever) so that the spray can flow easily between the vanes. With the back of the wheel closed off, it will be a lot harder to get the paint all the way down in between.

As others have already mentioned, mist the paint, don't put it on too thick. If you are using two-stage paint, the color coat does not need to be glossy, just even. The clear is what provides the gloss (and is where you have to worry about runs)