In a medium bowl, mix pepper, garlic and onion powder, thyme, oregano, brown sugar, chili, cayenne pepper, smoked paprika, and cumin until thoroughly combined. Set aside.
Place your pork butt on a large cutting board, fat cap side up.
Trim pork if desired. Make sure to leave a narrow layer of fat (⅛-¼" thick) on the outside to protect the pork from drying out. Pat dry with paper towels.
Optional step: Slather a thin, even coat of yellow mustard on all sides of the pork so the seasonings stick better to the pork. Worcestershire sauce also works, or you can omit this step.
Salt pork and rub the entire roast with the seasonings, pressing down as you cover every inch.
Place in an aluminum foil pan and let it rest for at least an hour (or up to 24 hours) tightly covered.
When ready to smoke, take the pork from the fridge about an hour before smoking if time permits.
Fill the pellet grill's hopper with wood pellets and preheat it to 250-275℉ (120-135℃). If using a charcoal grill, prepare it for indirect grilling and preheat to 250-275℉ (120-135℃). Add hardwood chunks to the charcoal to create more smoke.
Place the pork butt directly on the grill grates, fat side up. Insert with an instant-read meat thermometer. Once the pork reaches 165℉ (75℃).
Remove from the smoker and tightly wrap it with butcher paper or foil. Or place it in an aluminum foil pan and cover it tightly.
At this point, you can add more pork rub, hot sauce, or any optional seasonings.
Put the wrapped pork back in the smoker and continue smoking until the internal temperature is around 205°F (95℃), or the pork easily shreds with a fork.
Remove the pork butt from the smoker and let it rest at room temperature for 45 minutes to an hour. Shred and serve as desired.