Girls always have all sorts of useful things for us to take and use on plastic.
In this case, you're looking for a 4-way buffing stick that a girl would tell you is for fingerrnails. Well, it's not. Obviously, it's for polishing plastic. The one I have has one side that's blue and pink and the other side is white and grey. I got it for 99¢ at a beauty supply store when my wife was buying hair dye. My Hobby store charges $4.99 for the exact same thing.
You can use it to repair the clear plastic's surface. In this case, you probably don't need to start with the roughest side (the blue side on mine), but perhaps the second roughest (the pink side on mine). Give the damaged area a good going-over, but go slowly because you're making the windshield thinner as you go. You may want to do this in the bathroom under running water. Most sanding sticks are somewhat flexible, so the inside of a windshield should be no problem.
You will be scratching the surface of the plastic, but you only need to go over the damaged part. Once it's uniformly scratched, go to the nest finer grain on the stick (the white side on mine). The finer grain will take out the bigger scratches, but leave smaller ones. Because of this, you do have to go step by step and not skip any sanding grits. Once it's aluniform again, go to the last grit, the smoothest (the gray side on mine), and finish it off. As you go, you'll see it clearing up again, and you'll be able to blend it in with the surrounding undamaged plastic.
Let me know if you have any questions.
