Contact the Rounders Association. There's quite a good DVD which has some techniques, I believe. Bowling action has to be smooth and underarm which limits the range of techniques, but holding the ball in four fingers with the thumb behind it is effective to give side to the ball if you flick the thumb as the ball is released. Holding four figers on the outside of the ball and the thumb on the insie, nearest the leg is also effective. Rotate the thumb back and the fingers forward as the ball is released.