I follow this method for mine. I cut off a stock, scrape some tissue off of the bottom to reveal the underlying gorgonin structure and then plug that into a drilled hole in a disk stuffed with epoxy. However if yours is a fan type I'm not really sure what you do.
"Frag" of the Month - Gorgonian Propagation Techniques
http://reefkeeping.com/issues/2006-10/fotm/index.php