I bought a note 4 off eBay a couple days ago, the metal edges were pretty banged up. I taped off the screen very carefully with painters tape, make sure the corners were taped perfectly, removed the back, then sanded the shiny surfaces of the edges with 1000 grit automotive sandpaper. Worked like a charm, phone looks brand new. If you decide to try this, just go slow, be careful, and pay attention. There are several spots around the edges where a piece of plastic crosses over the metal, I assume they are parts of the antenna, avoid those while sanding.