PLEASE NOTE!!! These motions are natural and will help free you from tension. Very small amounts of the motion described here can be added to your playing but please don't try to play like this all of the time. It's way too much motion and will distract your audience! Also, any violin motion...
Please note: I say in this video (2x) that the stroke is usually done in the upper half of the STRING, but of course I mean upper half of the BOW. Sorry, I was in a hurry!