JB... use about 5-6 oz of wood, set the smoker somewhere around 225-235F, and expect the pork to go 2hrs/lb to get to an IT of 195F. I recommend that you brine the butt for a good 12 hours or more before you rub and place in smoker. Put a juice pan down by the wood box to keep a little extra moisture in the smoker.
Although I suggest allowing 2 hrs/lb for the butt to reach 195IT, it will likely take less time...this is unknown variable ... sometimes 1.5 hrs/lb, sometimes more. Allow for the 2 hours so you can plan out the time and not find yourself at dinner with a butt that is not finished! Also, factor in another 2 hours for a rest period after the butt is removed from the smoker - double wrap the butt in foil and put it in a cooler to rest, with some heavy towels. If the butt finishes early, then you can extend the rest time. This rest time is critical to let the juices redistribute through the meat before pulling. So, for a 6lb butt, I will anticipate needing 14 hours from start to finish before serving.
Hope this helps...fire away with more questions! Good luck!