I would like to suggest you go the the American Donkey and Mule Society for your training information. They have been around for many years, have a lot of very helpful information about the long-eared equines and the special training they need.
http://www.donkeys.com/ADMS.html
They have all kinds of books, articles, and I expect video in some form to watch. You might find some of that same stuff, used in Ebay or the used books places too.
Horse people get fooled by the long-ears that look like they should be horses, but think in an entirely different way! Cause and effect in training steps are very confusing, because horse knowledge DOES NOT transfer to the long-eared equines. We had always heard that there are “horse trainers” and there are “mule trainers” when you have a youngster to be broke to a new skill. You don’t take the mule to a “horse trainer” because mule gets confused and the mule trainer will be disgusted at how “slow learning” the horse is.
Personally, I like mules, but would not own one again. I do not think as a mule trainer does, so am not “worthy” to own a mule. She was managable, but it was probably a good thing for her, that we sold her when we did. She didn’t get ruined in our hands. The Mule Man who bought her LOVED her, thought she was a TERRIFIC mule and did we have any MORE like her to sell?
The mule folks I know say mule has to completely understand what you want him to do, before attempting to try. Confused mule is NOT stubborn, just does not understand you. YOU must adapt to new methods of training so mule is no longer confused.
Along with that you need to understand than mules and donkeys are different in behaviours. Donkeys may be used as guardian animals in herds of calves, sheep and goats. They will move thru a flock or herd easily, no problems unless a canine shows up to chase/kill.
A mule will harass or kill smaller animals, they are bullies in many cases. My Grandma warned me about mules going after smaller things and hurting them from her farm experiences. Chased calves, colts, ponies, bit and kicked, would NOT leave them alone if pastured together. Well that changed MY view as I watched the young molly out “playing” with my dog in the field! It was TRUE, the mule WAS trying to kill the dog, but dog didn’t know it, thought the game was Tag!! Good thing that dog was FAST. Well that was the LAST game of Tag they played! Our eyes had been opened!! Mule went when she started attacking the bred ewes, JUST missed them as they squeezed thru the sheep gate. Mule was striking from a full gallop, reared and bucked when they got away. We had a little kid about ready to come out to the barn, could not take the chance of him getting hurt, so she went down the road to another home that APPRECIATED her more than we did.
All the really good mules I know, came broke and trained. Owners just enjoy them, really don’t add to the training. They do seem to work their way north from the middle states area, broke the best for riding mostly. Go where aimed, work with you or the kids. One was the BEST diving board when the kids went swimming. He stood unattended in the water as the kids climbed on and dove off, for very long times.
Good luck with your training program on the mule.