That is pretty cool. My mom raised/trained horses most of her life. She has had to let them go now due to age and just being too beat up to do it anymore. When she was training a new colt to load in a trailer she would just pull the trailer out in the pasture and leave it open. At feed time she would place their food in the trailer and just walk away. After about a week she would close the trailer up and only open it at feed time. It didn’t take long and they just associated the trailer with getting fed and would walk right in when you opened the doors, lol of course the only downside was if we were cleaning the trailer out after a trip and we opened the doors we would sometimes have visitors walk in while cleaning.