Check out the link on EasyCare's website that includes tips, photos and special links that will answer your questions on natural hoof care.
Typically a mule has longer hooves than a horse. In addition, they also have steeper angles and larger heel bulbs. The biggest challenges you will face when booting are sizing the boot, getting the gaiter to fit over the heel bulbs and determining what can or cannot be adjusted. Using a smaller heel strap has worked on several occasions.
Proper fitting is the most important thing to remember after a fresh trim. The boot for a mule would be too wide if the length exceeds the width by more than one boot size on the sizing chart.
You will find me at the front desk if you visit the EasyCare corporate headquarters. I am in charge of the web orders and I manage the Hoof Boot Upgrade program which offers discount pricing on boots.