Sparse pasture tells me he would benefit from Vitamin E. You could order Elevate in powder form and feed several grams a day for a month or so and get his skin headed in the right direction. Then move back to 1 or 2 gms/day. Better yet - Elevate’s liquid E would get in his system even sooner.
My 28 yo Cushings guy barely gets groomed and looks great. I test my hay and balance minerals and also give 4 oz flax/day in addition to 2gms Vitamin E daily. And feed loose salt. 2 TBLS /day.
I still say easy improvement is the Microtek Spray and no more currying. He’s probably sore. And make sure to keep him dry until you get him healing. No rain or moisture - use a rain sheet.
That’s what I would do.