>>1230761dont use calf hair, it looks good, but it's slippery and you will hate trying to tie with it. the most popular one that i know is antron or poly yarn (like mcflylon). it also doesn't have to be white, i see orange, pink, and other bright posts a lot to make it easier to see the fly in the water, but there are a lot of things you can use as posts. im sure the fluffy couch stuff will do, i've used bleached turkey flats, egg yarn (like on this #16) and ive seen poly yarn, antron yarn, calf hair, foam, cdc, zylon and any number of things used. probably the easiest is the yarns though, and antron or poly yarn (like mcflylon) are the easiest to use. here's a video on parachute posts that might help
and again, in a pinch, the couch stuff will work.
https://www.youtube.com/watch?v=ifASrZHth9Q 