Yeah, I think the foil is the key step - I do 3 hours uncovered, two hours wrapped (add some apple juice or cider or apple cider vinegar with some water to the foil), then unwrap and finish with some sauce after they firm up a bit. The last batch I was in a hurry for at the end and firmed them on the grill (and had a fire on the dark end of the rack when I wasn't watching). Still want to do another batch on the WSM when I can be around to get the vents set correctly in the beginning. So far the kettle grill has been much easier to maintain a good temperature range (225-250).For BB's I do a modified version of the 3-2-1 method you hear about all the time and they have been turning out PDG if I do say so myself.
2 hours on the grill (1 hour each side) then wrap in foil for 2 hours, (this is what makes them fall off the bone tender) and then unwrap for the last hour to tighten up the bark. They may only need 15-30 mins more depending on how hot your fire is so no need to cook any longer than to tighten as they are more than done (tender wise) when they come out of the foil. Also I spritz apple juice on them about every hour or so to keep moist and especially spritz hard when they go in the foil to make more steam. Since I have a two tier grill on my Kamado I put a pan of water on the lower grill for added moisture and to act as a heat deflector for the meat as well.