I think you're doing the right thing with the "head tossing = work" approach. Also, any time your horse tosses his head, he is resisting pressure. Hold the pressure on the reins until his head is quiet, and as soon as his head is quiet, even for a few seconds at first, release the
rein and reward him. It may help to anchor your hand of the saddle or on
your leg when he is tossing his head, so he can not pull your hands
around and give himself a release from the pressure that way. For more horse training q and a, check out www.horsetrainingquestions.com.