Try to not give him any food for about 12 hours, only water,
and then give him some small amounts of cooked white rice
and boiled chicken. It is important that he only take a small amount (a couple of spoon fulls at most). If the diarrhea appears to be resolving, feed him the bland diet every 3-4 hours, increasing the amount fed slowly. After 2-3 days, if his stools are firmer, you can switch him back to his old food.