I do my own as well. Have been for about 25 years. I start by splitting the quill. Then I cut to rough length, a little more than 5 inches, and sand down the quill a bit with the feather hand held in a straight clamp using a disk sander. I use that clamp to hold the feather and make one pass by the sanding disk on a jig to even the quill base. Made a vertical clamp that I use to run the feather by the disk sander again, this time in the vertical position to sand the sides evenly.
Takes a bit of time and effort, but given the price of natural barred turkey feathers nowadays, well worth it. I ask all my turkey hunting friends to save the primaries for me so I usually have quite a few to work with.