I started out with the Mothers headlight repair kit. It comes with some polish and a Mothers ball thingie that fits on a drill. It also has some small sandpaper at 800, 1000, 1500 and 2000 grit. I worked on Nancy's car first and used up the paper so I went out and got all four of those grits of wet sanding paper to do my car. You start by taping off the painted parts of the car so you don't sand any paint off. I used that low tack blue painters tape. Then I started out with 800 girt and just sanded in a north / south motion. I went with an east / west motion when I went to the 1000 grit, and alternated with the 1500 and 2000 grits. I finished off with the Mothers polish and the ball on a drill. They turned out really well. You can tell the age on the side markers, some micro cracks, but they are really clear now. Makes a huge difference when driving at night.
I may end up getting new Cobra clear lights and markers along with some trick switchback LED side lights, but for now this is a good fix.