I'm looking for a bar mounted filing guide to start sharpening my own chains which I've never done before. I'm looking at three models. A) Oregon Professional Bar Mounted Filing Guide Reviews on Bailey's seem to suggest it's been around forever and it's good. B) Granberg Precision Bar Mounted Filing Guide Reviews on Bailey's say it's good but has poor instructions and is not the easiest thing for a novice to use. C)Stihl bar mount filing tool Haven't read anything about it. My personal criteria is ease of use so I can actually learn how to sharpen properly. Any advice would be appreciated. Thanks.