I would just add some coconut oil to the food.
Benefits of Coconut Oil for Pets | Wellness Mama
Benefits of Coconut Oil for Pets | Wellness Mama
Just be sure it contains named fish on the label, some don't. And be sure of no flavoring, or lots of other added ingredients. A lot of them do. I use one from Walmart, for humans too, and its pretty basic.Omega 3 fatty acids do wonders for skin and coat. You can just buy human fish oil capsules (way cheaper than what's advertised for dogs) and either put the capsules right in the food, or break them open and pour it over the food. My dog weighs 50 lbs and his dose is 900mg of EPA, so the dose for a ~70 lb dog should be about 1200mg. Just make sure to check the mg in EPA, not DHA.