I recently fixed a PS3 disc which had became damaged on the label side. There were many scratches both large and small with some looking like a starry sky. I figured the disc was trashed anyway so I wanted to try an idea I had.
I took a small paint brush and a bottle of Testors 1146 Silver Gloss enamel and painted a thin coat over the damaged areas. After allowing the paint to dry, I tried the disc and now the game plays.