Kevin Bacon http://www.kevinbacons.com/en/dressing.html stuff is meant to be good
We've used Equine America Hoof Power Plus with good results
but of course you could just try a magnesium supplement, or a biotin supplement, apple cider vinegar or seaweed ( a lot cheaper and probably just as effective)
A friend of mine coats her horses hooves with cod liver oil and swears by that.

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