I am pretty sure he was using wrist slings, (rope loops around the wrist) as well as a handle much like whats on the starter rope of snowmobiles.
Being an amature stunt kite flyer these are nessesary as the pull can be greater than your hand could handle. Even with my small kites, they can easily pick my 200lb a$$ off the ground for a short ways.
Yeah, when I went kite surfing with my cousin, there was a little hook that placed over the top of the bar. You kind of have to push it down and in to get it off the bar when the wind is pulling hard. ...dumb.