Combine all of the ingredients for the rub in a small bowl and set aside.
Trim any excess fat off of the tri tip and liberally season with the dry rub.
Start your smoker on the lowest heat setting (mine runs about 175-180 on Smoke) and place the seasoned tri tip on the grill grates. Close the lid and smoke for 3 hours.
Take the tri tip off the grill and place a cast iron skillet on the grill grates. Turn the temperature up to the highest heat setting (at least 400 degrees) and allow the grill pan to preheat.
Place the smoked tri tip in the grill pan and sear on each side for 4-6 minutes. Use an internal thermometer to monitor the temperature of your tri tip. Pull the tri tip off the grill at 120 degrees for rare, 130 degrees for medium rare, 140 for medium.
Allow the tri tip to rest for at least 10 minutes before slicing against the grain. Serve immediately.