John,
It looks like a bodkin but has three prongs instead of one. You stroke the CDC fibers until they are at 90 degrees from the stem. You then insert the very tip of the feather in between the prongs and roll up the feather along the stem, leaving you with all of the fibers clumped together sticking out from both sides of the tightly rolled up stem. Fold the rolled up feather in half (if you want all of the fibers. If you just need half of them don't fold it in half), clip the tightly rolled up stem off, and tie in the clump of CDC fibers (or tie it in first and then clip the stem. This seems to sometimes keep the fibers together easier). You can use almost every bit of every fiber on the feather.
I hope this is understandable. Maybe someone else who has one can describe it better than I.
Joe