We have a 9 year old pit bull (adopted at age 4) and we have only ever fed her no-grain food. For years we used Blue Wilderness ($60 for the biggest bag), but recently moved to the country and at our local feed & seed store we found a no-grain brand called Triumph that she loves just as much, and it's half the price!! Currently she's eating Chicken, Sweet Potato and Pea flavor, and they have lots of interesting varieties and very similar ingredients. I'd definitely recommend checking if you have a feed & seed in your area.
Otherwise I've heard great reviews about raw meat diets, but they are too time consuming for us to prepare.
I do make treats for her out of spent grain (we are homebrewers), whole wheat flour, peanut butter, coconut oil and eggs, and she never gets tired of them. Coconut oil can be great for a dog's skin and hair.
Finally, I find that if I brush her regularly it really helps her coat get smooth and shiny, because it removes old hairs and dead skin cells and allows her beautiful hair to shine!
