Mix the rub ingredients in a small bowl. Massage the mixture all over the roast. Allow the roast to rest at room temperature for 30 minutes before grilling.
While your roast is resting, light the charcoal for your grill and soak 2 handfuls of hickory chips in water. You'll need enough charcoal for a medium hot grill , about 350 F to 450°F For a 22 inch Weber, that is about 30-40 briquettes. In addition, you'll need a method of lighting additional coals to add during the cooking process to maintain the temperature of the grill.
When the coals are ready, divide them in half and push each half to opposite sides of the grill. You'll cook the roast in the center using indirect heat. You may also place a small pan in the center, between the coals, to catch the drippings. Add water to the pan to prevent the grease from smoking if desired. Drain excess water from hickory chips and place chips directly on charcoal.
Grill the pork butt until the meat is very tender but still juicy, about 185 F to 190 F, turning every hour or so. Grilling time will be 5 - 6 hours, so you will need to add additional hot coals to the grill at least once during the process.
When done, remove the pork from the grill and cover loosely with foil. Let rest for 30 minutes.
Warm 2 cups of your favorite prepared barbecue sauce, or make your own.
Pull the pork into shreds using your fingers or two forks. Combine pork in a large bowl with enough sauce to moisten. Mix well and serve on toasted buns topped with your favorite coleslaw.