I'm pretty sure only Hobbs wool batting is guaranteed not to beard, but it doesn't come in black. With any other type of wool batting, you probably want to encase the batting in cheesecloth before layering. This was the "old-fashioned" way of preventing bearding. Wool battings are *notorious* for bearding, so you probably want to research this seriously before making a purchase.
I found the following info which might be helpful to you:
http://www.masterstech-home.com/The_...attingFAQ.html
The only reason (I think) to use a black batting is so that, if the quilt is dark and the batting beards, the bearding is less noticeable. My choice would be the Hobbs wool even though it's not black, because it's not supposed to beard.