How to befriend a scared, shy, bitey dog

This dog is in his fourth home, he's four years old. Just getting him to take food has been a challenge, and sometimes that's just how it is. The amount of time that goes into rehabbing an abused dog is at least months, if not years.
It is challenging and rewarding at the same time. The amount of time, energy, and emotional work that you put into a dog like this creates a very deep and meaningful bond, but it's also not for the faint of heart.