I use a pump up sprayer and tap water warmed to my ambient temp which is 81F - 82F. I live in a very dry climate and have to spray most tubs every day to keep the humidity up. A lot of times I'll spray the snake directly especially if they are going in shed, but I'll avoid spraying the face / head so they don't breath in water. I would think you want to avoid little or no air circulation in the tubs to the point where it keeps the humidity high all the time, I think a good wet / dry cycle every few days is important to keep fungus and bacteria at bay.
