Combine 19 cups water, 9 tbsp table salt, and 4.5 tbsp dextrose in a large pot.Note: This is based on using 2 birds - if you only have 1 bird, use my calculator to determine your water, salt, and sugar. Submerge 2 whole young chickens (~3-4 lbs each) in brine.
Cover and refrigerate for 16-24 hours - do not go longer than 24 hours.
The next day, remove chickens from brine and rinse in the sink.
Pat dry with paper towels.
Place on wire rack over plate or baking sheet and air dry for 2-4 hours or overnight on the bottom shelf of your refrigerator.
Make rub. The main "stuff" are the smoked paprika, salt, onion + garlic powder, and black pepper. If you don't want to use MSG, don't. Same with cornstarch (used to avoid clumping). 3.5 tsp table salt, 1 tablespoon smoked paprika, 1/4 teaspoon garlic powder, 1/4 teaspoon onion powder, 1/8 teaspoon table ground black pepper, 1/8 teaspoon MSG*, 1/4 teaspoon cornstarch
2-4 hours later or the next day, truss chickens with butcher's twine.
Apply a thin layer of neutral oil to both chickens as binder.
Apply 1-2 tsp rub to each side of both birds (I start back side first).
Place on rotisserie and set grill to 325-350F with infrared back burner and first and last burners on medium.Note: This will be different based on your setup. This is how I did it on my Monument gas grill. Check breast temperature after 45 minutes with instant read thermometer.
Target 155-160F in breast meat.
If not done, return to rotisserie and check every 15 minutes until target temperature reached.
Remove from rotisserie and rest for 5-10 minutes.
Slice and serve.