A few random responses:
I usually brine pork if I have time (anywhere from a few hours up to three days), but it isn't essential. I make the brine with sea salt, brown sugar, cracked peppercorns and smashed garlic cloves.
When I use a dry rub I pat the meat thoroughly dry with paper towels, scrub the rub into it liberally,
then slap a layer of oil over that. Much easier than trying to spread a dry rub evenly over a slippery hunk of oiled meat....
I soak my wood, whether it be chunks or chips. I want it to smoke, not burn up. But you don't need to see smoke for the entire cooking time; the wood will keep flavoring long after the smoke stops being visible.
I also let the surface of the meat warm up before starting the smoke; it seems to keep bitter-tasting components of the smoke (like creosote maybe?) from condensing on it. But by warm I mean 'warm,' not 'after it starts really cooking.'
I've never tried mustard on Boston butt or a pork shoulder. But it works surprisingly well on beef brisket, and I see no reason why it wouldn't be good on pork too.
I'm addicted to mesquite and ironwood; I use it for smoking just about anything. But pork does well with smoke from citrus trees, plum and apricot trees, and probably any other fruit trees....
If you're using a smoker with a decent-sized water pan (like a Brinkmann), cut some veggies into good-sized chunks and add them to the pan: potatoes with skin on, onions, bell peppers or pasilla chiles, carrots, celery, garlic, etc; maybe even whole mushrooms. The steam from the veggies will help flavor the pork, and the meat drippings will certainly flavor the veggies.
Sometimes when I'm smoking pork I'll pull the pan of water and veggies when the meat is done, set it on a burner, thicken it with some flour roux to make gravy, adjust the seasonings, and slice the pork right into the pan.
The pan goes into the middle of the table as a serving dish with a ladle, a fork and a set of tongs in it. Uncouth? Probably, but no one has ever complained....
