I've had good luck with both the Oxygen Hoof product and Farriers Formula. The hoof needs to grow new hoof to be better quality hoof. Something topical might keep it soft and keep if from cracking but it's not going to fix the problem that is causing the poor hoof to start with. You are better off spending your money and fixing from the inside out with a supplement than going topical (although topical won't hurt!). You should see a difference from just one trim to another.
What happens is not as important as how you react to what happens. -Thaddeus Golas