I continued tacking up and standing on the mounting block and leaning over Shadow with my whole weight until he was ok with me doing that. I repeated this several times on both sides so he didn’t become set in one way that starts behavioural issues.
I began hopping on and hopping off. I put the bridle on Shadow after I’d already taken it off, just to show that he is happy to have it on again. Passing the leather over his head and mane without delay. He showed no fear, didn’t freeze, his ears were alert, his eyes were happy and his body language was relaxed.