DH watched CA's trailer loading episode 2x, tried it on our (now) 6yo KMH when he was being reluctant to load, and now he walks right in. It's what Bridgertrot suggested. Look it up, and maybe buy CA's fundamentals. TB's are never tied at the track and other basic training is ignored in an effort to focus on speed. You'll need to fill in your TB's training gaps, and there are many, unfortunately.