I'm currently working with PLA, for what it's worth. I recently put some parts and a few rafts into my rock polisher for 24 hours to see if I could do some post-processing like that. I tried a variety of dry materials and slurries (including toothpaste) but honestly, saw no positive result. (One attempt with some recycled rock grit polish merely stained the plastic so that was no good.) I'd like to revisit this with better abrasives. Was thinking sand, glass beads (from sandblasting media), diatomaceous earth, pellet pins, shot/B.B.'s and baking soda, basically anything harder than the plastic itself. Tried using sandpaper but it doesn't feel to me like the sand itself is hard enough for the job. Haven't tried wet-sanding, though. Haven't tried compounding cream yet. Ideas?