No, you do not need to spritz the pork shoulder if you have a drip pan with water in it in the smoker. A spritz is a liquid that is sprayed onto the meat in intervals of about every 30 minutes to an hour after the first few hours in the smoker. The spritz is to replace moisture and attract smoke to the surface of the meat. The downside to spritzing is that you are frequently opening the smoker lid, which fluctuates the temperature, and it will also cause the cook to take longer.