You need to know that you don't want to get him back to perfect health in a day. It took time for him to get into that condition and it will take time to get him out.
The big thing he needs is protein. Feed him raw meat, bones, and organs from a variety of animals after slowly introducing him to variety. Feed him about 3% of his ideal weight/day of food. Feed mostly meat, some bone and some organs. The exact percentages aren't important. You should begin to notice a change in a few days. His teeth will improve almost with the first meal and his coat will improve quickly.
You don't have to worry too much about water as there is a good deal of water in his food. As always, he should have water available all the time.
EDITED TO ADD: Oh, I forgot to answer one question. I would feed him twice a day, assuming he is an adult or close to adulthood. So that would be 3% of his ideal weight/day divided into 2 meals.
