Use effol on your horses hooves, it's an ointment and I recommend putting it on before every ride. My TB used to have stress fractures in his hooves and within a day of using the product, the stress fractures reduced
Dover saddlery sells stuff called turpentine and it works super well
To prevent cracked heels, I advise you to take a great care of your horse's pastern.
You absolutely need to rince your horse's legs, dry it and avoid as much as possible friction between the horse's skin and his equipment.
You can also use a little bit of paraffin.
Some of our costumers showed us great results using DERMAPROTEC! It is a very great balm which protect the horse's skin.