Another thing I learned from Dan Quillian: an old FF string cut into 4-5" lengths and inserted into the string works very well. Unravel the string after it's installed. The more you shoot, the more it fuzzes up, getting better all the time. It's so light that it doesn't affect performance like heavy rubber spiders and the like. I used 21 strands on the one I made this week.
I've used yarn, but in my area there are too many weed "hitchhikers", like beggar's lice, that get in the yarn. I've had them hit me in the face when I shot and they popped out of the silencer. They don't stick to FF.
In emergencies, (another Quillian thing) you can loop a big rubber band onto the string, and pull it back over the bow tip so that it bridges the gap between the string and the bow. It works very well, but tends to hang in the brush.