The carving knife got about 80% of the job done but to begin to refine the shape I found the best tool was a large rasp. The rounded side was useful for carving inner curves and the flat side good for smoothing out planes and surfaces. With any complex three dimensional shape you are going to find places that are almost impossible to get at with any kind of sander, but a neat trick I read about and used with modest success is to hot glue sandpaper to paint stirring sticks. I also hot glued sandpaper to 1/2" and 1" diameter doweling which was useful for sanding small inside curves. With these sticks you could reach in and sand places your hand could never fit through.