Hi Back foot slider,
Thank you for your kind words! I'm glad you like the exercises.
The rebound force is what you should be looking to maximize (heavier and heavier ball) followed by the quick explosive concentric action of the arm (the throw). So that transition TIME to the throw (on the throwing rebounder drill) is what you should be looking to minimize. Minimize the time the ball is in your hand, but use a heavier and heavier ball to progress and force the body to adapt.
Naturally a faster throw will happen because you're trying to shorten that amortization phase, but it's not really the emphasis. Throwing harder against the trampoline will cause greater force for the rebound coming at you, too.
Prescription wise...we're trying to create power, so for starters I go no more than 8 reps for 4 sets---waiting at least 90sec between sets to allow for recovery. Because the total volume is "higher" (relative) at this stage, I would do this every other day. After 2-3 weeks of this, you can progress to 2-3 sets of 5-6 reps with heavier and heavier ball. Because the volume is "lower" now, you can do this daily, taking 1-2 days off/week from it.
Be sure to watch the player doesn't have poor form at their elbow when throwing 
Is that helpful?