PS, i'm not looking for "call the farrier" answers, im looking for ideas on what I could try in the meantime. Thanks:)
As leaving walls too long is one major cause of cracks, and keeping them regularly & well trimmed is one of the necessary ingredients in treating them, unless you are looking for 'learn to trim yourself' answers, I'm afraid you won't get far without good farriery.
I wouldn't bother about 'moisturising' and cold, dry ground is not a problem, except in considering that if the walls are overlong, the harder the ground, the more leverage forces will be acting against the disconnected wall.
Good hoof care is a rather holistic affair and diet is about the biggest single factor. 'Natural remedies' include good, well balanced nutrition, low-cal, low starch diet, ensuring the horse isn't allowed to become fat and keeping him well exercised. Booted or otherwise protecting his feet, so he can *comfortably* use his feet *correctly*(eg heel first impacts) & therefore develop their health & strength. Oh, and especially if there are cracks/separation, contracted frogs, etc, etc, regular treatment/ preventative measures against infection are also important, as it can eat the healthy tissue as fast as it grows & perpetuate cracks, sensitivity, etc.
Hoofrehab.com is one great, comprehensive site, with a heap of info & links on other factors of hoof health aside from farriery. Barehoofcare.com & barefoothorse.com are 2 of many other good sites to get you started learning about hoof function & health.