POLISHING SUN DAMAGE FROM HEADLIGHTS.. AND PLASTIC MOONROOF?

I was reffered by a GOOD source to get 2000 grit sand paper and water. I did that some on the bad spot on my headlites. They leveled out and are not clear. What makes em clear. Do I have to compound and buff them, polish? or something else?

Also have another car with a plastic sunroof panel also in need of this treatment? What is the best process please.