I use an auto body rasp...takes about 5 minutes per head...
First thing you do is flatten the non-bevel side, because its not FLAT until you do.
Then change your bevel angle.
Then a 14 inch Nicholson files the bevel side, then the other bevel side, then lay the file flat on a table and re-cut the flat side again.
At this point, you'll see the "foil" on the edge of the blade.
Using smooth sided leather mounted to a board with glue, strop the broadhead back and forth, gently, till you see that foil edge peel off like an orange peel and S T O P
She's ready.