Slather the yellow mustard all over the surface of the meat on all sides. This will help the rub stick to it.
Coat all sides with your rub, massaging it into all of the crevasses.
Set up your smoker to 250℉. Place the pork butt onto the hot smoker and smoke until the internal temperature of the meat reaches 165℉, about 3 - 4 hours. Every hour, use a brush to mop on some of the vinegar sauce.
Remove from the smoker and wrap in a double layer of heavy duty aluminum foil or butcher paper.
Place the wrapped pork back on the smoker at 250℉ and continue to smoke until the internal temperature of the meat reaches 205℉.
Remove from the heat and let rest, wrapped, for 30 minutes.
Pull the meat apart into chunks, throwing away any clumps of fat that did not render. Serve and enjoy.