I used Myler bits after running into the Myler brothers several times. I played golf with one of them years ago when I still played golf. I found that a plain smooth snaffle worked fine for nearly everything. I have used hackamores on mules in a big arena to work on legs cues and seat bone cues.
A mule out of a Missouri Foxtrotter mare, was broke and good minded, but didn't have much of a handle. She liked to chase one of our geldings. I used to ride her with the mecate reins loose on her neck. Right before she was going to turn right chasing the horse, I would give her strong leg cues. Pretty soon she got much lighter. She would stop without touching her face just by sitting on the seat pockets and saying whoa. One spring day, she was frisky so we loped down the beach by a lake at high speed. I said whoa and gave her the cues. She left skid marks for many feet. Not bad for a mule with no handle. The mind of a mule is a like a lock that needs a key. You have to find the key and they are all different.
