I got a RainX restoration kit at the Bargain basement about a year ago. NIB at a fraction of the retail cost. Though it just what I needed to rehab the headlights on wife's 01 van.
Followed the directions and the result was that it made very little improvement. After reading this thread, I figured I needed to start coarser, so I did.
Worked the lenses over with Comet cleanser, rinsed and hit them again with Bon Ami. Made a big difference. Might do that again and then try the RainX kit again.