Although the palm and forearm can't ACTUALLY work up the front of the barrel, especially with good I/R, that thought helps to train the wrist and fingers to work the ball UNDER and THROUGH the ball vs. pulling across the ball........And thinking about trying to gain/maintain some wrist flexion into/through release also helps the fingers work under the ball.........
I really like the barrel idea... I've been using a hula hoop for years... and I hate answering to people why there's always one in my car. I'm thinking the barrel will look better... maybe a cask...