Oh no lol not another one of these
I have two of these ones...
The first is my 16.1hh gelding mitch, who was always trucked as a race horse.. We tried everythig from leaving him there to pushing and using ropes in his mouth and chains over his nose... Nope. Nothing of that sort worked with him, he would literally stand there quiet patiently waiting for some magical front door to open up so he could walk on out. Sorry bud, that aint happening and your a bit big to turn around.
He actually tried turning around one day and managed to cut his head and one leg, slip on the float mats, hurt his back and fall out of the back of the trailer.
So one day, I loaded him up in the float and hooked up two lung lines to him, gave one to my dad and said Pull. And by god we hauled that horses butt right out of that float, did it a few more times and he understood.
He's been to a few shows since then etc, and he has only needed one reminder.
The thing I can not stress enough, is to stay calm and patient. It gets very hot inside those floats if you are stuck in there with a stubborn horse (or the likes), I remember sweating like crazy, even though the day was not overly warm.
It is really good to have a helper or two on hand also :) good luck