dropping the shoulder

Whiz -2, wants to drop his rib and shoulder to the left, while loping around the pasture in a large left circleI I kept playing with his face, trying to pick the shoulder up and he wasnt taking me serious, kept dropping out of lead, dropping the shoulder and finally I got tired of babying him and swatted him on the right "buttock" as my children are learning to call it. It scared him a little but ultimately it seemed to help him pick that shoulder up and run properly in the circle. It wasnt a matter of driving the hip to the left and shoulder to the right, it seemed to be more of a matter making him quit doddling around and drive his but with impulsion. Jack Brainard makes mention of this in his excellent book.