Trail riding if possible. I ride a hot mare named sassy and she's definitely a go go mare, all we do with her is slow work and making her walk ( she doesn't like it and often try to trot and lope/ dart to run, but after a few sessions she can now walk the whole barrel pattern . It does help
As much turnout as possible. My Morgan used to be stalled 24/7 and was a monster, now he is out for 8-10 hours a day and is the best behaved horse in the barn, nothing else changed. But also lots of mental stuff when working, circles, serpentines, zig zags, transitions, keep her engaged mentally at all gaits so she can't just freight train around.
Lots of slow but mentally engaging work, such as small figure eights and zig zags at the walk.
Hi Baille, I train horses that are Hi strong and what has worked for me is that when I start my session is always at a walk and stay at a walk until I feel like they're ready to work and I'm comfortable also throughout and at the end of the session.