If you can do a backroll transition already it's just a small step to a backroll handslide. The backroll handslide is a trick every kiteboarder should have in his pocketlist...
Love the tutorials of this guy...one of the few who also talks about kite position and making it visual at the same time! Really one of the tricks you should be trying in your next session (maybe not in NL...it's freezing over here)