Here is my tip on the water pan.
1. Foil the water pan completely with HD foil.
2. Foil a 12" clay flower pot base completely with HD foil.
3. Place the foiled flower pot base inside the water pan.
4. Place a 12" disposable foil pizza pan inside the flower pot base.
Each cook toss out the foil pizza pan and replace with a new one.
This way you have a clean grease free cooker every time you smoke and you don't waste foil. I only refoil the works about 2 times per year.
Temps remain much more steady with the clay in there. This is especially important when it is windy.
I have never used water.
Haha, you don't waste foil but you throw the foil pan away each time?
I do not think the clay pot, sand, or any other material is useful in maintaining temps. Once it is heated up, what good could it possibly be? Water is understandable as it absorbs a lot of heat when vaporizing, and the 212F vapors fill the smoker and keep the temps down.
I'm smoking in mine right now. I have the water pan in there, but no water. I think this is the way I'll run mine from now on. Tomorrow I'll just dump the water pan/grease in the woods, hose it off quickly. Easy.