Information from Jarek about the ball:
Jarek: Best size for the ball is as a basketball or football! To lern the form I think basket or football is the best. Then for practice and some power building a heavier ball is better, so who wants can look for a medicine ball or bowling ball best size is ca 30-35 cm.
I`ve put on yutube some exercises with ball http://www.youtube.com/watch?v=RzKArSvOdKw&feature=youtu.be