How dirty of a car will this work on? I have a Black ZL1, and live in Pittsburgh and drive it daily. Will it safely clean a car that's trashed with road salt and grime? Currently, I wash it outside wearing cold water dive gloves(scuba gear) and then dry it in my semi-heated garage. You know how easy it is to screw up black, but this would be much better if it will safely clear all the grit without scratching. And why used double soft towels rather than the wash pads? You input will be appreciated, as always.