I've found that running the water over the trough and making a mud hole helps the most with dry feet. I run it over every day so they are in mud every day when they drink.
Are they cracking because they're just dry (need a moisturizer) or because they're brittle? If it's a dry summer sort of issue, I like Cornucrescine Hoof Dressing or Moisturizer (and I like their Barrier when it's wet). If it's general poor hoof quality or brittle, then I'd use some Keratex Hoof Hardener and maybe start on a hoof supplement (I like Farrier's Formula).
I like the Straight Arrow Hoofmaker. And the mud is a good idea. Just soaking the feet with water helps. I hose Pepper down on days that it's really hot and then apply the Hoofmaker to his wet hooves. This helps seal in the moisture. You might want to add biotin to the diet, also.
I'll start leaving mud holes while I'm watering them. I'm trying to avoid giving a supplement as the feed they are on I feel have made their hooves healthier, its just been so hot and dry here and plus I live in a rocky area didn't help any. The one thats worse he was at the trainers for several months in a stall and since being back his feet look a whole lot better but the cracks are pretty bad.
I've had my farrier out this morning and he said my other 2 aren't as bad as I thought but the one could use a little help and he suggest mud as well and if I want to use a hoof dressing just use it once a week.
Are you talking about cracks in the bulbs from the heel up? If so, I get that with my QH.
I have a syringe (no needle) with a hook on the end. You can get it anywhere they carry tack/feed of just use a regular one, no needle of course. I stick in in the crack and flush it out. It hurts so I do it quickly. Usually takes about 3 times. Debris will come up most likely or ookie junky smelly stuff. I use water or peroxide to flush. Once I know I have flushed it all out I dump some neosporin in the syringe and squeeze it in there. You really need to get it up in there too to do any good. If its bad, I'll then pack gauze in it too. I'll use a hoof pick or the end of something sharp to get it in there. Super OUCH! Sometimes instead of neosporin I'll use thrushbuster. Just depends. The gauze will work itself out in time so don't worry about it. You can also use some Bag Balm rubbed into the back of the hoof itself too if you want to make a huge production out of it. Then you can wrap it all up with a stay free mini pad for comfort and then vet wrap and stall the nice horsey for a couple of days on clean bedding. Again, shoving all that stuff in there is not fun so expect resistance. Give sympathy and carrot treats. Keep out of the mud and keep it cleaned up in there.
If you are not talking about the crack that goes up into the bulbs, then sorry I'm a dummy.