I used to work in a glass shop. Cerium Oxide powder, buffing pad, water and a lot of elbow grease. I would use this to buff out scratches on windshields. Run your finger nail over the scratch and if it gets caught inside it's too deep and buffing it out will cause a distortion and might be more noticeable than the scratch, it can be done but you have to find the midway point were the scratch is less noticeable without distorting. Light scratches are no problem and can be buffed out in no time with less pressure on the buffing pad like you would need on something deeper. Do this outside because you will make a mess with all the wet powder.