I'll start with about 280 grit sandpaper and a cork block to flatten the surface and level the binding:
This fingerrest goes on a vintage instrument that has a finish which is amber from age and ultraviolet exposure. I'll be spraying it with amber lacquer to match the original finish, so I won't be sanding with anything finer than 208 grit. Later, I'll sand it level with 600 grit used wet, and buff it as I would a lacquer finish on a guitar.
Here's that mitered corner:
I bought the narrow black and white already laminated, so I mitered the corners when I glued them on. The ivoroid outer layer is thick, and just laps over at the corner. You can't see the joint because the Duco cement melted and "welded" the pieces together.
By the way, here's the effect of not protecting the surface when gluing up:
See the dimple in this Gibson mandolin fingerrest? It probably didn't show up until the finished buffed piece had been sitting around for a while.