I have found that if you use a 1/4 to 5/16" hole maybe 1/2 to 3/4s deep and fold your brush material in half and force it in you don't need any glue or whatever. Start with more, thicker and longer than you need, use a little dish soap to get it to get it to slide in easier, wash it good, let it dry and trim it.
Never used Turkey beard, mostly horse tail.
Tim C.