3) They are incredibly quick to learn, but do not react well to pressure.
THIS. This point is key. Typical pressure/release training that one might use on a horse will not work well with a donkey and only serve to make them more resistive.
The key to good donkey/mule training is to find what motivates them, and use it.
Donkeys are smart and learn quickly, but the trick is to keep them willing. Don't try to force or push anything on them, you will be taking steps backwards with that approach. Keep training sessions short, light, and fun. Make training time something they look forward to.