you realized that wall don't hit back, right?
try yoga ball against the wall? while wearing pink leotard?
In a pink leotard, I don't have to move at all. The sight of me knocks them out.
However...the yoga ball...a friend of mine got incredibly strong and immoveable since I had seen him and he is doing "only the soft stuff" including "universal exercise," "pole shaking" and pressing some kind of inflated ball, about the size of a soccer ball, but softer, against a wall and moving it around...not clear what he was doing with that, but he got both very soft and very strong.
So how do you use the yoga ball? What size?