I bought an inexpensive kit designed for use with a drill (<20.?). Took me an hour to restore 2 very yellowed lenses on our Honda toad, including very noticeable gravel damage caused by many miles of toad duty. They still look great, with no further treatment, 2 years later.
No doubt which way I'll go next time. Even if somebody had given me a free set of lenses it would have taken me longer than an hour to install them...
1997 37' HR Endeavor, 275hp Cat, Freightliner
03 CR-V Blue Ox, Ready Brake