I am working on starting my mini donk for harness this year. We're getting the verbal commands down for "walk on" & "and whoa" really well when walking in hand. However, trying to teach him to lunge at a walk & I'm getting no where fast. He does not understand that I want him to stay away from me. I try to stay behind his shoulder to drive him forward & he does everything in his power to get back just behind me. He wants to do the typical "nose to tail" donkey single file. How do I get him to understand that he needs to be out & away from me?