I've had good success success with players and a machine like this...Hold a ball in the opening of the chute with my right hand. With a ball also in my left hand, extend my arm straight up, and hold there until the batter is ready. To feed, I bring my left hand straight down and bump the ball in the chute into the wheel. I have found that using a 2-ball method drastically minimizes feed errors and provides much more predictable launch timing. All the players I have worked with (my DD's teammates, 10U-14U) have had no problem with this method and their full swing process. Being consistent with the pre-launch timing is important.
