Start off by making the brine. In a large bowl, add in 8 cups of lukewarm water. Then mix in 1/2 cup salt and 1/2 cup brown sugar. Use a whisk to mix everything together until the sugar and salt are dissolved.
Then add in 6 boneless skinless chicken breasts. Make sure they are fully submerged under the brine. Now place it in the fridge for at least 2 hours, and no more than 6 hours.
In the meantime, make the spice rub by combining 4 tablespoons brown sugar, 2 Tablespoons chili powder, 1 Tablespoons smoked paprika, 2 teaspoons onion powder, 1 Tablespoon garlic powder, 2 teaspoons oregano, 1 teaspoon salt, and 1/2 teaspoon black pepper.
Once the chicken is done brining, remove it from the brine and pat it dry using paper towels. Then season both sides of the chicken with the spice rub.
Now add some applewood pellets to the smoker and preheat it to 250 degrees Fahrenheit and place the chicken directly on top of the grill grates. Smoke the chicken for about 2 1/2-3 hours or until the thickest piece of chicken reads at least 165 degrees Fahrenheit. Use an instant-read thermometer for this step. Tip: you can use apple, cherry, or applewood pellets for this recipe.