Brown sausage in a large skillet. Add flour and cook until flour browns just a bit. Add 2 cups of milk and stir, then add 2 more cups and stir, add remaining milk if needed and bring to a boil and keep stirring. If the mixture is not thick enough mix 2 tbs. of flour and 1/4 cup of milk, then add to gravy. Simmer for 5 minutes and serve over biscuits.