You need someone else to do the second hit, it's a teamwork thing. You can't stun then hit before they can defend again.
Although if you can stun someone without them realising and they try to hit back, you can double hit them. Stunning is also a good lead in to kicks, stun then kick takes a lot of the risk out.
Although if you can stun someone without them realising and they try to hit back, you can double hit them. Stunning is also a good lead in to kicks, stun then kick takes a lot of the risk out.