I have used the clay bar many times (granted, on a white car). I used extremely watered down Armorall in a spray bottle for lube. Also, I would rub the clay bar in the same direction as the lines of the car. Same with washing and drying. God forbid there was a chance to leave a mark maybe from a not so clean chamoise or grit on your bar, the lines wouldn't be as obvious as if they were in the opposing direction. My $0.02. Please don't blast me if you think otherwise.