Watch the nick wheelers part of the bowie series on YT on the handle shaping. One of the things he says is people switch way too early to soft backed sanding paper or shoe shine method. Keep it backed with a file or a piece of hardened steel 97 percent of the way. For curves you can use half round or round files. This helps also with not washing out the lines on your handle if you have ridges, flats and similar. When sanding hard and soft materials, concentrate on keeping the sanding part of the file always on the harder material to not create that bump. This happens with pins as well.