Ah, the good old "beating stick!" (don't worry we don't really beat them) Solo broke my brand new purple jumping bat when I smacked him in the butt too hard. (He was being a butt just because newer riders had been letting him get away with things all week.)
Generally, it he fails to pick up the gait I'm asking in 2 strides, or if he's a liitle slow coming to a jump, I tap him on the shoulder as a wake up call. If he's continually being slow or thinking of refusing or doing something bad I smack him in the butt.