For some reason, Cushingoid dogs are more prone to pancreatitis than normal dogs, so it will be important for you to keep your dog's diet very low in fat. You also want to keep the food low in fiber and high in potassium. Cushings medication makes it difficult for dogs to digest high fiber foods properly, and high potassium diets just give them more "oomph" when dealing with taking the necessary medications.
What medications does you vet have your dog on?
Ghilly
Really your best idea is to consult with your personal
vet,they would know what type of diet is best for your
fur kid as well as offering information on what to do.
Jan