I've done butts for many years. My techniques can be found in the forum's recipe book from Eggtoberfest 2004 (see the link below). I've done those butts at Eggtober fest for 5-6 years now.

In a nutshell, a brine is a form of a marinade. The primary difference is a brine is designed to get to the entire piece of meat, whereas a marinade is designed to soak into the outer portion of the meet.

Marinading after brining will either make the butt too salty or waste your time. When you brine it, the butt will absorb the contents of the brine until it comes into equilibrium with the salinity of the brine. If you then tried to marinade it, the marinade would have to be saltier than the brine to get the marinade into the cells of the butt.

The best balance between the two is what is known as "flavor brining". This involves adding something other than salt to your brine solution. When smoking butts, I add moleasses (some folks use molasses, but I prefer the added depth of flavor provided by them moleasses! (grin))

Also, don't just smoke a single butt. If you've got a medium, you can smoke 2 or 3 at once. With a large, I can get 4 or 5 on the smoker. Pulled pork freezes really well (especially when sealed up with a Food Saver), assuming you have any left overs (which is why I smoke as many as I can at once!). It doesn't take much more time to prepping an additional one or more butts and I haven't seen an appreciable increase in the smoking time.

Oh, and make sure you use a rub. That really enhances the flavor of the bark (Bark - definition - outer layer of the smoked butt that is left in the kitchen because only the cook has the discriminating taste buds necessary to appreciate the best part of the butt!)