If you really want to control your temps for bbqing and smoking and want to remove the guesswork from airflow, get one of these:
http://store.thebbqguru.com/weborderentry/DigiQ%20DX2
I use it on my Big Green Egg and it can hold temps perfectly. I've also used the Smoky Mountain and its a great smoker, it is what is used in this class:
http://www.cookbookcooks.com/class-s...cue-workshop-0
I would recommend that class to anyone. Since taking it I've greatly improved my slow bbqing.