Similar products have been discussed here before and tried by some users and have not done anything. there was another product someone used that did work well. (it actually had a clear coat to apply)
I have restored quite a few headlights over the past year.
My method is to sand down with 1000 followed by 2000 then 3000.
Then using a plastic polish such as Meguiars Plastic X to buff up to near new condition. If your buffing by hand it will take a good solid hour on each light or if you have a machine buffer, use on around 1500-2000rpm and never spend too much time on one area so you don't burn the plastic.
Another option you have is to sand down then clear coat them to give extra protection.