Not used VPA heads but for Snuffers and even the Grizzly Instinct 3-blades I use a Mill File (Nichols) and lay it flat across two blades at a time and stroke them with same pressure and count...then rotate and do same to next ones...then again on third set. Then I lower my count and pressure and do it again...all three times...until I get down to very very light strokes for a 2 count on each rotation. Usually they are pretty dang sharp at that point. The key for me is after the first rotation I lighten up on pressure so at the end I am taking much less off and really just refining edge and putting burr on it.
After this I go to some leather and draw the head backwards across leather a few strops on each side...and they are ready. Touch ups in field or through season are with an AccuSharp carbide...again VERY LIGHT pressure.
Being consistent with count, pressure, stability and angle of file and being able to repeat it so you are not working against yourself is important.
Good luck.