I've read in the past that products such as the creams or sprays that you use to polish wooden and leather furniture or other products that contain a wax ingredient of some sort, when applied and polished off several times with a soft cloth, can help to fill in scratches.
I'm not entirely sure if this is true or not but it's the best I was able to come up with in the past when researching how to fill out some scratches on glasses. Hope this helps you out some.