Dear All, i would like to change your mindset first. For good skin and haircoat condition following things should be there: hair cell get nutrition by the blood supplying at the root of hair follicle if supply is continuous then hair will get nutrients. So first thing to keep in mind is blood supply to hair. New Skin cells keep forming everyday and older cells sloughed off. During this process certain chemicals are formed that are harmful to healthy cells, actually they kill healthy cells by the process of oxidation, this results in loss of strength of skin so it may cause flaking of skin, hairfall because skin hold the hair, more chances of skin infection to flare up like mange , pyoderma or ectoparasitic infestation becuase skin is loose so ticks or fleas or mite have easy access to suck blood. Finally there are certain nutrients that are important for a healthy skin and haircoat like Sulfur and Zinc. So ultimately these three things you have to keep in mind and then design food for your dog.
Let me know what you understood then i will tell what you should feed.