You can also add fats that will help the coat by trimming or reserving the fats from meat, including bacon, that you eat. Just go easy on bacon fat due to to sodium in the stuff, a teaspoon or two per week for a 30-40 lb dog is plenty if you are giving 2-3 ounces of other fats or, a tsp of oil everyday. Mix it up, oil, bacon grease, a little meat fat, a 1000 mg fish oil capsule broken over the food, a vitamin E capsule broken over the food. I've given all of the above with no problems when the bulk of the raw diet I feed is venison and rabbit - both very lean so, a bit of added fat is needed to maintain the best coats and, insure the dogs can use all of the fat soluble nutrients in their food.
Nothing wrong with a dog food that contains grain, corn is simply one of the hardest for a dog to digest so, it's mostly a fiber filler, like you eating All Bran Cereal, it fills you up but, the majority of it is not digestible so, just bulks up the stool. Rice is a better grain and, for a dog preferably white rice.
Feeding partially raw isn't expensive, if it's like where I live, you can buy chicken leg a thigh quarters in 10 lb bags for around 50 cents a pound. That's about the same cost as cheap dog food and, adding even one leg or thigh per day for each dog will provide some benefit and, they will enjoy it. Just debone all of the larger bones (the small ones in there are okay to feed but, the big ones in legs and thighs can break into pieces with very sharp ends on them so, shouldn't be fed except to dogs with very strong bite force.) NEVER GIVE A DOG COOKED BONES OF ANY KIND OR SIZE. (Cooked bones splinter and break into sharp pieces a lot more readily than raw bones.) Obviously raw chicken can't be the only thing the dogs eat but, slowly working it up to 25 to 30% of their diet would benefit them and, it should be affordable for you.