I did a level and crown once using pretty crude tools (many years ago). The results were less than stellar. One issue I had, and maybe it was the lighting, was in knowing when a fret is really properly rounded over or if the sharpy line has just been scratched off. I mean, if that fat sharpy line is just touched with a file, the sharpy in that area is removed, but that doesn't mean that the area has been properly profiled to the line. I guess one way to approach that would be to start at the top, filing something of an angle to the sharpy line, then profile toward the bottom. This seems to be the opposite of what I see everyone doing though.