I have used Williams waterless wash/wax for some time. I had the same miss givens as yourself i.e. you will be rubbing dirt picked up on the cloth back into the paint and therefore scratch the finish. However this has proved not to be the case, I spritz one panel at a time, rub with a microfibre cloth which remover the dirt , polish with another cloth and finally buff with another. My daily car is a Merc e320 in sparkiling lridium Silver and the paintwork has suffered no damage by using this product. I dont think it saves much time from the sponge and bucket method but you dont need to get the hose or pressure washer out and you dont get wet feet! I dont think this product offers the protection of a good quality wax such as Autoglym and I still use this at intervals. You need quality large microfibre cloths and you have to wash them afterwards.
