For Pork Butt we always smoke a Bone-In butt. The bone helps the butt in many ways and if you are not sure when it is done the bone will tell you. First rinse the butt and pat it dry, then wrap it in cellophane. Take a marker and mark the cellophane with a dot on the places you want to inject. I usually make a 1 1/2" grid. Mix up an injection made of the following:
3 1/2 C Water
3 TBSP Amesphos
1/2 C Caro Syrup
1/8 C Plowboy's Yardbird Rub, finely ground
2 TSP Accent
1/4 C Apple Cider Vinegar
Now inject the butt at the grid points. Let the butt rest in the refrigerator overnight. Take the butt from the refrigerator and pat it dry. Slather a thin coat of yellow mustard on the butt. Rub the butt with mixture of 2/3 cup Plowboys Yardbird rub and 1/3 cup of sugar. Place the butt in a 225* smoker. We use a combination of apple and cherry to smoke with. We usually add apple juice to a spritzer bottle and give the butt a spritz every 1 1/2 hours. When the butt gets to 160* pull the butt, sauce it thoroughly with Head Country BBQ Sauce and foil the butt. Put it back in the smoker until 180*. At 180* pull the butt from the smoker open the foil and put about an 1/8 of a cup of strained Stubbs Pork Marinade in the foil and fold it back up. Put it back into the smoker until 200*. Remove the butt and open the foil. Rest it for 15 minutes because we do not want it to cook any longer in the foil. Fold the foil back up and wrap it in a towel and rest it in a dry cooler for 1 1/2 hours and you are ready to serve. We usually pull chunks from the butt and glaze with some Head Country BBQ sauce thinned with a little Apple Juice and serve the money muscle as glazed slices.
This is how we do it. You will see a lot of teams do it differently. You can always substitute you own favorite sauces and injection. Good luck with it.
FYI: We always use a Thermapen but you can always tell when a butt is done by tugging on the bone. It it turns and removes with minimal effort the butt is done.