I've used Meguiar's waxes and car products for over a decade in professionally detailing cars.  Had tried another brand's high priced 2-part headlight lens refinisher on two different cars (1993 Mustang, 2007 Expedition), using a buffer as recommended.  Within a couple of weeks, they both were turning cloudy/yellow again.  Was immediately impressed with PLASTX;  easy to apply and remove by hand, and you could see the cloudiness/yellow immediately disappear (I used two light coats, removed in between, just to be sure).  Lights look nearly new and are bright again.  Also used on the taillights to return their glossy appearance.