Thanks for asking a good question that as a new leathercrafter, it took me some time to perfect. I will usually contour my edges with my beveler; wet down the edges with water before I use a very fine sandpaper "sponge." I then sand the edges (all in the same direction, very important). Once I feel comfortable with the the edge, I will either wet them down with water or gumtack and use a Cocobolo slicker. The friction of the slicker will cause the edges to turn out slickly smooth. I did start out with a circular plastic slicker from Tandy, but I now perfer the wood slicker. I heard Deer antlers work well for a slicker, but I have never tried one. I did read that you should wear a mask when sanding or drilling on an antler due to something harmful in the antlers.
Oh yea, make sure you dye or color your edges before you slick them. This is just something that I do with my edges.
Good luck!
ATX