Having thought about desensitisation, about how much is desirable? Or about what sort of a horse do I really want?, here are some more practical and immediate ideas on training methods and the thinking behind these from Cathrine Fodstad again:
https://www.ridelikeaviking.com/post/what-to-do-about-spooky-horses
https://www.ridelikeaviking.com/post/what-to-do-about-spooky-horses