Hi so I was helping another friend train her horse a beautiful but stubborn blue roan gelding. He knows how to lead, and stand when tied. So we were trying to train him to lunge and he caught on very quickly and was doing great at a walk but when I asked him to trot, by tapping his rump with a whip and kissing to him, he stopped. I asked him to trot again and he just half-reared and started going backward.
What should I do?