After this got hung up in my head I had to see if I could build one. Was hoping to use a 45/70 cartridge for the main barrel, but didn't have an appropriate size piece of tubing that would allow a snug fit for that caliber so ended up cutting the neck down on a .300 Winchester Magnum and using a piece of 3/8" stainless tubing. The .300 mag can't be "loaded" (pun intended) with as much hair, but it seems to be plenty for what I'm doing. The pictures are pretty much self explanatory and while this thing isn't pretty it does work. The last picture is a bit fuzzy, but you can still see that the hair is nice and even on the end.
It's an easy build that took me less than an hour and that was including finding all the parts.