i use the four 0000 steel wool. they sell it in most window cleaning supply shops. and or your hardware store. its like a pillow and it never scratches the glass. unless you get a tiny rock stuck in it and your smashing to the glass, so change it often. i could go through 1-2 pieces per residential house. sometimes ill steel wool every window on a job if the glass is just way dirty. i charge a little more and the quality is great.