Preheat your oven to 300F. See notes below for slow cooker method.
Cut the pork shoulder into 4 smaller pieces. If there's any string around the roast, take it off. I don't remove any of the fat.
In a small bowl, stir together the brown sugar, chili powder, garlic powder, smoked paprika, salt, cumin, and pepper. Coat the pork pieces in the spice mixture, and add them to a Dutch oven. If desired, you can do this step the night before and keep it in the fridge, covered.
In a small bowl, stir together the chicken broth, Worcestershire sauce, and liquid smoke. Pour it around the pork.
Cover and cook for 2 hours, then uncover and cook for another 1.5 hours or until it's fall-apart tender.
Take the meat out of the Dutch oven and place it on a baking sheet. Shred it with two forks. Ladle some of the leftover cooking liquid over top to moisten it a bit, and toss to coat.
Serve in toasted buns with BBQ sauce and coleslaw. To toast the insides of the buns, heat a tablespoon or two of olive oil or butter in a skillet over medium heat, then add the buns and watch them closely until the insides have browned nicely (do this in batches).