This video from the Illinois BBQ Society on YouTube.com takes you through the in's and out's of the WSM and the ProQ Excel. For those that wish to reduce the cooking time for the pork butts, wrap them in a double thickness of foil after they reach 170 degrees internal temperature and it will save you several hours of time. In my WSM, I can cook two pork butts in less than 9-10 hours by foiling in this manner.
For any type of cold weather, the less you open the bullet smoker, the easier it is to maintain a consistent 225 - 250 degree cooker temperature. With an uninsulated cooker, this becomes more important in cold weather. You'll also use less charcoal.