I've seen the suggestion to use paint brush fibers as cheap "May Fly Tails"

I specifically notice that the brushes I grabbed
from the barn seem to have stiffer fibers than "micro fibbits" and I wonder
about them making flies poor hookers ??

The correct spelling is "Microfibetts." I mention this not to be a
critical snot, but to make the point they are named for, and by, John
Betts--MicrofiBETTS, get it?

Some years ago I read an article in which John Betts said he got the
idea for Microfibetts after making tails from paint brushes for his
own use. I infer there's little or no difference between brush
bristles and Microfibetts.

But you gotta use (at least in most cases) bristles from ARTIST'S
brushes, not house-painter's brushes.

They are kind of expensive, but I watched the Michael's (craft store)
ads in the local paper until I spotted a half-price sale on artist's
brushes. I bought three--white, tan, and darker brown bristles--for
about twelve or fifteen bucks. I have a two-lifetime supply of tails.

vince