Since I do not have a belt sander,I use a large 16" file, magic marker and cardboard. Usually start with 15 strokes, (back to front with the BH mounted on the shaft.) per side. Doing two blades at one time. Then I go to 10X per side, then 5,4,3,2,1 per side. Once I get to one I make another 20 strokes/side getting lighter with each passing stroke.
This usually gets me VERY sharp, shaving hair with no problem.
Recently here on TG I learned about stroping with a piece of corrugated cardboard. Pulling the head backwards 12X per side.
Now my WW are scary sharp!! I have never gotten a head so sharp!
I am keeping them in the garage b/c they are too dangereous to have in the house!
chris <><