If they are the original montecs good luck trying to shave hair. Due to the bevel on those heads I was never able to get them shaving sharp despite trying several different stones, etc. The new CS version is easier to sharpen. In my experience montecs fly great but don't leave much of a blood trail (possibly due to being hard to sharpen).
We set a file at an angle and use an old arrow for a holder. The file sets in a block of wood that has a slight angle cut into it. File it until you get a "beard" or "fine wire edge" on the blade. Then use a leather strop or paper wheel sharpner until the beard goes away. You will have it as sharp as it can get.
Or, another method would be to use the diamond flat that G5 sells. It won't make them as sharp but will put a decent edge on them.