I assume that since you say he is spooky, that for the most part he is trained but doesn't react well he is fearful. Desensitize him to as much stuff as you can, walmart bags are great running them all along his body until he stands quietly, small tarps along his body also putting them on the ground and having him walk across it. My friend starts all this on the ground first, walk them through trees where the tree can touch him, walk them through ditches, if you can find water walking them through that, even puddles make some horses anxious. Jumping up and down, waving your arm around the front end of the horse. Touching lots of touching. I put the saddle on and pat the saddle all over lift the stirrups and let them fall back into place. Do all of this on both sides. We mount our horses from both sides as well as dismount. Youtube has a lot of stuff type in spooky horse exercises and you will probably find all kinds of stuff. Have a great day