basically everyone uses oils or greases sometime in the year in aus, because its so dry and the ground is so hard, our horses hooves crack etc.
Yep, just paint it on, all over the hoof.
We have heaps of different types of hoof things, some are mane from animal fats etc, some from different types of oils and some chemicals (not good lol)
They all basically do the same job, strengthen and moisturise the hoof to prevent cracking, crumbling etc.
We also have hoof seals, so in winter etc they don't get to soft.
Really depends on the brand and whats in it but generally as I said before they are to prevent cracks.