This is the way it was explained to me.
"To make the tail, loop a piece Of chenille around a hackle feather, put the loose ends in your vise, take your hackle pliers and twist from the bottom loop while whisking the barbules out, when it's tight loop the chenille up to your vice and unclamp while holding the new loop together. The chenille will twist into itself and you'll have your tail."
The top half of the jig I spun the hackle in the same way as the first but not tight enough to roll over itself, then wrapped in like regular chenille and then tied off.