I have found the speed of the sanding discs is critical for the 3m kit. My cordless drills were not fast enough and left swirls. The corded dewalt produces much clearer lens, but you have to be careful not to overheat the plastic by pressing too hard or staying in one spot too long (don't go there
). You also have to clean the sanding discs every 20 or 30 seconds to keep them actually sanding.