This method worked for my dogs and they never experienced any diarrhea. I generally buy Nutiva brand virgin coconut oil. It's solid a room temperature. Princess will eat a solid glob like a treat. Carly is picky so I have to warm it until it's liquid and pour it on her food.
"Solid or liquid coconut oil can be added to food at any meal or given between meals. The optimum dose for dogs is about 1 teaspoon per 10 pounds of body weight daily, or 1 tablespoon per 30 pounds. These are general guidelines,as some dogs need less and others more. But don’t start with these amounts. Instead, introduce coconut oil a little at a time in divided doses. Because coconut oil kills harmful bacteria, viruses, parasites, yeasts, and fungi, the burden of removing dead organisms can trigger symptoms of detoxification. Headaches, fatigue, diarrhea, and flu-like symptoms are common in humans who consume too much too fast, and similar symptoms can occur in dogs.Even in healthy dogs, large amounts of coconut oil can cause diarrhea or greasy stools while the body adjusts. Start with small amounts, such as ¼ teaspoon per day for small dogs or puppies and 1 teaspoon for large dogs. Gradually increase the amount every few days. If your dog seems tired or uncomfortable or has diarrhea, reduce the amount temporarily."
Link to article: http://www.cocotherapy.com/wdj_coconut_oil_article.pdf