Use the right ring/3rd finger to hit the skater packet, just below half way works for me. Also, remember to sort of follow through with the ring finger- if you just stab the packet, the packet won't really spin much, or it'll spin so fast that you lose control.
Finally, allow the weight and momentum of the packet to spin itself round.
Hope this helps. It's really something you'll need to experiment with as there is no tutorial out there. I, and the vast majority of people ou there who can do it have watched videos of people doing it and tried experimenting with the move.
-Ben Woodhouse