The parts I polished on my phaser still look great. I polished the nozzle barrel, dilythium crystal clip, the bands along the side of the P1 and the fins in the back of the P2. I think I posted how somewhere way back in this thread. The only part I had a problem with was the thin metal clip in top of the P2 in front of the P1. It's got some sort of paint finish that just scarred up and didn't take a polish.
I did all the polishing on the assembled phaser, masking off the areas around the parts to protect them. I seem to recall someone popped open the phaser bodies and discovered they were sonically welded together. So you won't be able to just snap them back together. Splitting the case might also trash the electronics.