If the wheels do not have any greasy hand prints or oil on them, they may be ready to spray. I don't like wiping down sandblasted items as the lint from the rags I use sticks.
The DP90 is good stuff, I would use a reducer, as without it may not flow well at all out of our spray gun.
The featherfill would be considered a top coat, just make sure that DP90 has flashed, as the temperature is critical to the time frame as well. I usually add a bit more time because I spray at cooler temperatures.
If you must clean the wheels before priming/painting, then any degreaser like simple green or a detergent mixed with water will be fine. In that case, I would dry with a torch in order to make sure there is no water sitting in a crack/crevasse.