I would use warm water and dry completely. Like another said, you can use a blow dryer, not all horses like it though. My palomino loves the blow dryer. You could also use baby wipes, like another said. If he has sores from the diarrhea, don't curry it off, otherwise it will hurt and he may object. But if he is tolerant and doesn't have sores, you could brush it off like you do with dry mud. Good luck!
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We're not dead yet.
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