We got best improvement on our catcher by getting close enough to force a rapid response, or get hit by the ball, and a series of varied throws.  High left, low right, center fast, high slow...<p>Take a bucket of balls and just run through them quick.<p>This seems to align with the study.  Same basic task, lots of minor, well in our case occasionally major too, variations.  The kids would improve notably and significantly in a single session.