Preheat your smoker for indirect grilling at 250 degrees F. Use hickory, oak, or cherry wood/pellets for the best flavors.
In a bowl, combine the salt, pepper, and garlic powder. Pat roast dry then lightly rub olive oil all over for your seasoning to stick. Season your chuck roast liberally on all sides with the rub mixture. When your smoker is to temperature, place the seasoned roast on the grill and cover.
Smoke the roast until the internal temperature reaches 165 degrees F (this took around 4 hours on my smoker). A nice dark bark on the exterior of your roast should appear at this point. Wrap in foil and return to the grill until the internal temperature is 195 degrees (approximately 1 more hour).
Remove the wrapped roast from the grill and allow to rest for 15-20 minutes. Cut into 3/4 inch cubes and transfer to a foil baking pan. Sprinkle with 1/4 cup brown sugar and drizzle with most of the BBQ sauce, reserving a couple of tablespoons for later. Toss gently to coat all of the pieces in a little of the sauce.
Place the pan on the grill, close the lid and cook for an additional 1 1/2 to 2 hours, or until the sauce is bubbly and the cubed bits of beef are falling apart tender, stirring occasionally (every 30 minutes or so).
Sprinkle with the additional 2 Tablespoons of brown sugar and the remaining BBQ sauce. stir gently and return to the grill for just a few more minutes until everything is well incorporated. Serve hot as a main course and try not to eat the entire pan before the rest of dinner is done.