After one day my Sandisk Sansa Fuze has (old version) smooching with my keys in his pocket, I wanted to try to get this thing back on track. My first attempt was already a while back and I have been doing is trying polished out the deep scratch exclusively with diplex - which is about as much fun as trying saw through a piece of wood with dental floss. After further internet research I have now, however, the trial started, first to edit the thing with 3000 grit sandpaper and only afterwards with diplex - and it worked extremely well (see my review of appropriate sandpaper). First, I have this thing about grinding for 30 minutes with occasional wetting the sandpaper (important!). After I did it then polished about 1 1/2 hours with diplex. Although after a few minutes first superficial successes can be seen, it takes quite a long time, despite the preparatory work to bring all the microscopic scratches from the player. The supplied polishing cloth looks cheap, it probably is, but it works well - had in between short time a Brillenputztuch tried, but that was too thick, so that it has absorbed too much of the polish. With the supplied polishing remains where it belongs - on the display.
Overall, the polish has worked very well with me, so even 5 stars. But you have a lot of patience, experimentation and craftsmanship bring - otherwise the will nix. In addition, I would be informed in advance if the means for the device is suitable - otherwise you do hire more damage than heal.