I generally estimate at an hour/pound and keep the temperature around 230F in the egg. I use a dual-probe no-name thermometer I picked up at Sur La Table for $30. There are several great rubs out there, including the ones mentioned above. Dry the surface of the butt then wipe it down with plain yellow mustard then liberally add the rub. I usually wrap it in plastic wrap, and let it sit on the counter for several hours to bring it up to room temp prior to putting it on the smoker. The mustard helps adhere the rub and wrapping it allows the mustard/rub combo to turn into a sort of glaze that crusts well during smoking. At 160F internal (meat) I wrap the butt in foil, and at 195-200F I remove the butt and place it in a cooler and cover it with a heavy (beach) towel. After an hour of resting, remove the butt, drain the liquid from the foil, shred the butt, add the liquid back to the meat. That liquid is the sign that the fats and connective tissue have broken down and the meat should just fall apart. Without the foil wrap for the last few hours, I've found that the meat dries out considerably more as the fat breaks down and falls into the smoker.
I stick with pecan or apple wood. I've had a few bad experiences with Hickory leaving a bitter and acrid taste on the meat, same with mesquite.
PS. The mustard is just a binder, there is no real mustard flavor left on the meat. I say this bc I generally despise yellow mustard and greatly questioned how it would affect the flavor when I was advised of this method.
