Keratex is amazing and works fast
I use Smartpaks smart hoof ultra supplement. It worked really well for me and my trainers horse. My horse was a rescue so she had terrible hooves when she got here. They were cracked and chipped so I started using smartpak and they are so much better now.
For a topical use - lanolin is great to create a harder but moisturised hoof wall and sole. (Pure lanolin, not the mixed stuff)
+1 for Biotin, and you can get hoof strengthening tar which helps boost Biotin I found
Feeding biotin is very effective.