I use one as well, but find it still leaves the base of the feather a little thicker than I like.
After igrind them, I cut to length and but them in a jig clamp and sand them down a little further with my belt sander.
I typically use factory white feathers along with turkey feathers, and the factory ones have a much thinner base, which caused some difficulty when I burn them to shape.
But for doing the lions share of prepping the feathers, this jig is the way to go. Fast and easy.