I've cooked a butt or two over the years; often times as not it's attached to the picnic to be a whole pork shoulder. I dont know how many, but I'm sure it's in the thousands (I'm old, and I'll cook them 10 or more at a time).
Most of the advice above is spot on. El Ropo, a lot of what you're referencing has to do with the specific smoker. I have one that doesnt come back to temps quickly, and I have another that cooks more like a convection oven.
Seriously, inject with something simple, like apple juice and worchestershire, perhaps a little of your rub mixed in there. Rub it down and put 'em on the smoker. Keep sweet blue as best you can (warming the logs helps). You dont have to spritz, especially if your foil. Keep 'er closed up tight and let 'er cook... When to foil (or if you foil) has a lot to do with both personal preference and how your smoker smokes. So that you dont end up over-smoking it, I suggest foiling around that 4th to 5th hour, regardless of internal temperature. You put fat cap up or down. We use fat cap down, but that has more to do with having to present the meat whole. Fat cap up works fine too. If you're looking for really awesome pulled pork, take the meat off the smoker between 195 and 200. Let it rest still in the foil for at least 1 hour, 2 hours if you can. There's a reason folks swear by this technique. If you dont have a temperature probe to test the meat temps, cook it for 9.5 hours at 250 IF you're foiling at 4 hours and IF you've maintained 250 mostly the whole time and IF you haven't spritzed. When you pick the meat up, it should have a little "give" to it. You can feel it's done.
Largely, keep it simple. Watch your temps. Keep it 240-250, you'll be very happy with the results. Oh, yeah, as others have said, that 8 - 9lb bone-in butt is pretty much the best. When you open that foil you'll be able to pull the bone cleanly from the meat, and you'll have wonderful moist pulled pork to burn your fingers on.
Best of luck with it.