Before you go into sanding polishing and a bunch of money and labor,try one thing many of us use.
Just plane old PLEDGE spray.
It worked so well for my original 83 screen,I bought a can to keep on my 88.
Just spray and polish both sides and ride.
Yup, Pledge does quite well. If that doesn't do it, Meguiars sells a kit for restoring fogged over plastic headlight housings that works pretty well - it's a gentle abrasive suspended in a gel, that helps polish out the scratches. I tried it on an old windshield that I was going to scrap anyway, and it did such a good job at clearing up the scratches that I ended up selling the windshield instead.
The above mentioned works quite well and if you have something any worse than mentioned above plastx polish works well too. But Pledge is for sure the first try.