I used to work at a glass shop years ago. If they are too deep it's not worth buffing because you'll just deform the glass buffing them out, like a fun house mirror effect. If your finger nail gets caught in the scratch then it's too deep. If they aren't deep and you want to buff them out practice on a spare piece of glass first and use plenty of water to keep the heat down and be ready for a mess. The buffing station at the place I used to work at was always a mess because of the splatter from water and Cerium Oxide.