Check out The Rebound Game.

What I recommend ...

Work with one hand at a time, focusing on allowing the stick to bounce as many times as possible. Challenge the student (and yourself) to think of throwing the stick and seeing how many bounces they can get out of one hand. Try to count the bounces. A great goal is to be able to get 8 or 9 bounces out of one stroke. You can then do this same thing, but going hand to hand ... a right hand stroke, then a left hand stroke. Getting as many bounces as possible from one stroke.

Taking this to the next level, creating the Buzz Roll ...

Play a right hand stroke, getting as many bounces as possible from that one stroke ... then start a left hand stroke BEFORE the bounces in the right hand stop. Before the left stick stops bouncing, pick-up and throw down the right stick again. Doing this very slowly, relaxing and getting as many bounces per stick as you can is the key to getting a nice Buzz Roll. Eventually you can decrease the gap between strokes, allowing more of the bounces from each hand to overlap, and get the finished Buzz Roll sound ... which sounds very close to ripping a piece of paper ... with no pulses coming from the stick strokes.

There are a number of other techniques that I use (and teach), but much of this would need to be done visually ... either in person or video.

Hope this helps.