The same candidate states he can "pop his initials down on a mule's behind". I believe long trains of mules in team were used, and a long-lashed whip was used to supplement the emphasis of traces and reins. Not as punishment which as anyone who has ridden a mule knows is directly counterproductive. More as incentive. You pop the tip of the long lash just offside their head and they pull off in the opposite direction.

The term skinner, I have always believed, meant someone who could manage mules, but derives from the concept that one _could_ pop the whip artfully enough to flay them, not that one would.

This is speculation on my part.