I work at a auto glass center and we have various ways of removing scratches. It really depends on how deep the scratch. The windshield is laminated so it will not take a lot of heat and one time. I will crack or distort if not careful while being buffed with a electric buffer. Buff, let cool, buff, let it cool, etc... Temperd glass will take the heat. Heat is what really removes scratches in which the compound makes the heat. If the scratches aren't to deep a good compound , damp towel, and some hard fast moving hand buffing will get them out. If the scratches are all over the glass for instance wiper scratches you will be better off to purchase a new windshield. The time you spend getting them out will just about justify a new windshield. You could take your car to a auto glass center and have them look at it and see what they say.
Older the windshield the more likely it will crack while buffing. Glass over time becomes brittle. Good luck