Reading back over the forum I think there were suggestions made (there is no single "answer" for the question):
-Stay hydrated pre dive
-Bring liquid cough drops/hard candy such as jolly ranchers for between dives
-Bring water and/or gatorade for between dives ... stay hydrated
-Take your reg out underwater and rinse your mouth
-Buy a $200 piece of equipment that no one has any personal experience with