Our first mini was Horsezilla... he'36 and 325 lbs. It was difficult wiith green children, and a green horse... but we did it... Lol.. Oh heck, I was green as green can be too. First my goal was to get him to accept wearing a saddle. I walked that boy 100 miles up and down the road with his saddle on, and he loved being walked like a dog. He had a halter on, and would love to sneak a bit of grass from time to time, and so he loved to go out for a walk, even if he had to wear his saddle. Now I have to say a few people tried to longe the boy.. wasn't happening. His previous owner DIED of a heart attack when he was trying to train him. (They didn't tell me that until after we purchased him). He just loved his long walks, greeting the neighborsd, snorting at the local dogs, showing his butt to local dogs... and frequently acting like a big mean donkey. He was alo also a four year old stallion at the time, and there are lots of full size mares in our neighborhood. Anyway, I walked him ,and walked him and walked him...
Finally, I put our 35 lb daughter on him, and put reigns on his halter. She couldn't begin to keep his head up and out of the grass, but.... we'd make sure he was on pavement, not near the grass. He still loved his walks. After six mos of walking him, and doing lead line exercises with our little daughter on him, we introducted the bit and bridal. Not his idea of fun, but by then it was routine that he take his walks... with all his tact. Repetition I think is the key for training any animal.
Anyway, with about a year and a half of being ridden by the kids, the 35 lb daughter (who is Ms Petite and now over 40 lbs), she does a 2'9" crossbar with him. Okay, so we're still working with him. Sometimes, he likes to cheat and go around the jump, instead of over it... and he does this twisty thing around the side at the last min. HE HAS NEVER DUMPED her in the dirt.
A while back, we were looking at some property, that had an obvious trail, and there was a 40 in fence, I was trying to figure how to get on the other side, without messing with the fence. Just as I was looking for the best direction in the trail to take... Horsezilla jumped the fence.. with the daughter on him.. never a spill.
It's more work for me to train a mini to be ridden, because I gotta do all this walking, but, well, without any experience training horses... I get it done. Darling daughter has now trained her sister's mini to be ridden, and has done all the work herself, in the front yard... She's only six years old.
When asked the question, how do you train a mini horse, I always answer. "It's just like training a dog, repetition, repetition, repetition..."
(If I wasn't so dumb, I'd post one of the pictures of her riding one of the minis.)