I buy Grobet files locally and use everything from 6" to 12". The little 6" goes in my bag for field touchup, the 8 and 10" are used to get and edge beveled properly and then sharp. I use a 12" on the rare occasion I want to sharpen a 3 blade cause I use 2 blade almost exclusively. When I get one sharp with the file, I then use a leather belt or a piece of cardboard to strop on for the final edge.
I bought a KME a couple years ago and didn't like it. It was too awkward for me. Also since I shoot wood arrows, I want to mount the head and shoot it to make sure it is flying good before sharpening. It was too much to try sharpening with the head mounted