How can I use this DMT diafold FFHWC sharpener for a knife with a hook (AKA hoof knife)?

The FFHWC has a hook groove specifically for fishing hooks. For something like a hoof knife with a curved blade they are going to want to get the Serrated Knife Sharpener. The name of the product might be a misleading, but this is designed to sharpen a knife with a curved or oddly shaped blade. It will allow you to sharpen along the edge continuously.

https://www.youtube.com/watch?v=vx91QFuyLrQ

https://www.dmtonlinestore.com/Diafold-Serrated-Knife-Sharpener-P32.aspx