After searching auto parts stores unsuccessfully for a brush long enough to reach through and scrub all the way to the back edge of the wheels, I made my own. I went to Home Depot and bought a refrigerator coil cleaning brush like the one pictured. I cut off the small end at the red X and screwed a plastic wire nut on to cover the exposed wire ends so they couldn't scratch the wheel. Voila! It works great. Try it.