Preheat smoker to 225 degrees with hickory wood or good quality charcoal. See my Smoking Meats guide for advice. Rinse the roast under cool water, then dry with paper towels. Trim the fat cap to about ¼ inch thick, then score into 1 inch squares.
10 pounds Boston Butt roast
Rub all sides with yellow mustard, then generously apply the rub, working it into all of the nooks and crannies.
1 bottle mustard, 2 cup Boston Butt Rub
Using a tray or roasting pan, place the roast into the smoker, and insert a digital thermometer into the deepest part of the roast.
Smoke at 225 degrees until roast temperature reaches about 155 degrees. This will take several hours depending upon the size of the roast. Baste with Carolina Mop Sauce once every hour. The roast should have formed a good bark by this point. 4 cup Carolina Mop Sauce
Remove the roast from the smoker, and wrap with 2-3 layers of heavy duty tin foil. Then return to the smoker, re-insert the thermometer, and continue to smoke until internal temperature reaches 195 degrees.
Remove from the smoker and rest for at least 10-15 minutes.
Shred the roast into a large bowl, mixing in any juices that have collected in the pan.