No, putting topical goops on hooves do nothing for their health, like painting your own nails may make them look prettier, but cannot make dead, impermeable tissue any healthier or 'moisturised'. 'Dry' is not actually the problem. Horses do best in dry environments & their feet are meant to be dry on the outside - it's inside the impermeable outer layer(periople) that the horn is moist. Topicals, especially oils or astringents can also do more harm than good. For eg. cracked hooves also often harbour infection, which if sealed in, will only help the bugs grow. Here is an online report of one study done into hoof goops; The Horse | Hoof Dressings: What Studies Show
It could be diet & nutrition that are at the root of his cracked feet. Especially if they appear dry & shelly it's often the case. It will take at least 6 months or more to really see any change in hoof quality from diet/nutrition changes. Most horse's diets are deficient/imbalanced in a range of nutrients, so do benefit from a good complete supp. While 'complete' feeds advertise themselves as 'well balanced', they're often not, aside from the fact that you've got to feed the recommended quantity to achieve that balance, which may be totally inappropriate for that horse.
Re supplements, if you're looking for a 'cheap' option, unfortunately IME you do tend to get what you pay for in relation to feed & supplements. Often I've found that the most 'expensive' aren't really though, as they're way better balanced, so provide the horse with what they need, instead of having to feed a variety of different supps. Also it seems that generally the more expensive, the more concentrated, so you need to feed so much less than the cheaper variety that it is more economical after all. Eg. many feed supps need to be fed in lbs or kgs per day, whereas for eg KER(Kentucky Equine Research) supps are vastly more expensive per bag than many, but you only have to feed approx 60-80 GRAMS of the stuff! Also re cost, I found that when you actually analyse what's needed, almost inevitably the amount recommended on the package is in excess of what they actually require - & may also have a lot of other rubbish that they're better off without. So IMO, the outlay that may be needed to analyse the horse's diet, nutrition & options of supps is economically worth it too. Eg. I think feedxl.com are a fantastic service/program & at $15 for a month signup for one horse, I saved HEAPS more than that in being able to provide my horses with exactly what he needed and rest assured I could get away with far less than the manufacturers suggested!
It could be mechanical - could be that his feet have been neglected or trimmed imbalanced, which is putting too much stress on the walls in that area. Could be that his heels are sensitive or some such, so he's putting too much pressure on his toes. Could be that he's been in an overly wet environment which has weakened his feet & caused them to crack when on hard ground. Could be that infection has got in to compromised wall material & eaten it away. It could be a combination of all the above. If you would like more specific opinions, some hoof pics & further info would be helpful.