Preheat your smoker to 225°F and add the type of wood pellets you want to use.
First, heat the beef tallow once warm fill your meat injector; I recommend adding about a cup. You can also use broth instead.
Lightly coat the chuck roast with olive oil. In a bowl mix together the beef rub - onion powder, cayenne pepper, garlic, and salt & pepper to taste and coat the roast. You can also use a store-bought rub if you prefer
Truss your chuck roast. This will help it retain its shape.
Place your chuck roast on the smoker and insert the temp probe. You want it to reach an internal temperature of 165°F before you move to the next step Place in your smoker uncovered once your smoker has preheated to 225°F and is burning a clean smoke.
Once the fat has been rendered, you will have a mahogany color, and it will reach an internal temperature of 165°F pull from the smoker.
Wrap your beef along with a smear of beef tallow on the butchers paper.
Return it to the smoker after wrapping. Smoke the roast until you reach an internal temp 203F-208°F. Test it by seeing if you can easily slide the probe in and out.
Rest the roast at room temp until you have an internal temperature of 180°F. Wrap again in pink butcher paper smeared with wagyu tallow and leave your cooler to rest for 6 hours
Slice the roast against the grain and serve with your favorite sides.