Takes a bit of technique, the polishing at the end is where i needed the porter cable (available online)
Check here for a good writeup on how to restore lenses. Can also search on Youtube or here for some videos. Really just tape it up and make a few passes with each grit (horizontal, vertical). Once you get to the 2000 it will look really fuzzy but the surface should be smooth. At that point use the plastX to polish it out. You could do it by hand but would need to use a bit more aggressive cloth to smooth out the sanding.