We went camping last week and hit quite a few gravel backroads. We've done plenty of gravel roads previously but when we got home we realized that the dust seems to be almost bonded to the aluminum. Hubby tried soap and water, elbow grease. I tried some Bar Keepers friend with a sponge (did some good). Almost impossible to shift this stuff - any tips on cleaning this stuff off? I am aware of Steve's post on polishing but assume we may need to clean first.