Every second person who owns a horse or mule knows a different way to put the steed in a trailer. Half of the "methods" work, half do not. I have had people come to my place in Malibu and spend half a day buying a new saddle, and then fail to get the horse back in their trailer after four hours of trying.
One lady finally left the horse with me, and a professional horse hauler arrived and I am glad she wasn't there the next day to see the method HE used. Wasn't pretty, but the driver was on a schedule.
Everybody has a method, but the problem is the more you rush that exercise -- no matter what method you are using -- the less likely you are to be successful.
Rush a mule and you won't even get to first base. Get physical with the mule and he will more than likely simply sit down, and stay there until HE is ready to get up.
That could be several hours.
A method that NEVER fails for me involves no actual handling of the animal, and no work. It is so simple it is ridiculous. Get your trailer, back it up to the gate or the door of the barn, whatever, drop the ramp, and thereafter ONLY feed the horse in the trailer.
I had a horse who refused to go in the trailer for a whole day, but I didn't blink. Next morning I went down and there he was, in his trailer, happily munching away. And that is how I fed him for two weeks.
From that day forward, whenever I opened the trailer door, I would toss the end of the halter across his neck and step aside before he ran me over to get in. He trailer-trained himself !
Which is a point I have explored HERE.
Do we train horses, or do they train us?