I normally blast the wheels with a pressure washer, then iron x when wet (i normally dilute it a bit in the bottle as well to mae it last a bit longer), leave for 5 minuted then pressure wash again. I do find that they do get dirtier quicker though, I guess as I don't wash them with shampoo they aren't getting any sort of waxy stuff that the shampoo might have in it. I have thought about using sealer too, but my life's too short to seal 4 19" multispoke wheels