I've used both picnic and butt. I love them both.
I plan 1.5 hours per pound but it is usually a tad quicker than that. If you don't have a smoker to do it then do it in the oven. Set it at 225F, rub up the shoulder, then let it cook. If you have a probe then use it, otherwise test it at the 1.25 hour/pound mark and look for 190-195F. Rest it for an hour in a big bowl covered with foil.
Take your time pulling it and get all the fatty glumps and the boingy bits out. Toss lightly with a vinegar sauce and then have more on the table for guests along with a good mustard sauce.