THREE BLADE METHOD.....
For three-blade broad heads I do the following:
First I go buy a "chain saw raker file" -- Oregon is a very good brand. Then I put a handle on the file.
I lay the file across the flats of two blades at a time and file pretty hard until I can feel the file "bite" into the metal for the full length. I will give each blade edge pair about 20 hard strokes this way, turning to the next pair of blades after 20 hard strokes.
Next I will count down by twos, in other words 18 strokes per pair of blades, then 16, then 14 -- still filing hard -- until I get to 10.
I then count down by ones with lighter strokes -- in other words 10, then 9, then 8 -- until I get to 6.
Then I really lighten up on the strokes and continue the count down method. Light strokes polish the blade edges.
When I get to one, I turn the blades after each stroke and give the head 21 very light strokes -- remember very light.
Next I turn the raker file to its side - the side of a raker file has no teeth, and acts like a butcher's steel -- and I give each pair of blades a stroke with the butcher's steel side of the raker file, turning to two new blade edges after each stroke. I give the blade about 20-30 light strokes this way
With the above method I can get a new woodsman or snuffer razor sharp in 5 minutes or so.
To maintain the edge, start again at about the 6 stroke level with the file and continue with file strokes and then file edge strokes through the countdown.
One tool, shaving sharpness -- easy.
Don't forget to put a handle on your file to keep from cutting yourself.