Combine the beer, salt, sugar, soy sauce, and black peppercorns in a large Dutch oven or deep tub* and whisk them together.
Place the chicken in the brine and add a few cups of ice. Fill the vessel with cold water until the chicken is completely covered, cover, and let the chicken sit in the fridge in the brine overnight.
When you’re ready to cook, preheat the Traeger to 375F.
While the wood pellet grill preheats, remove the chicken from the brine and pat it dry with paper towels.
Let it come to room temperature while you whisk together the salt, paprika, garlic powder, pepper, and cayenne. Rub the chicken all over with the softened butter and the spice rub, making sure to get under the skin.
Open the beer you’re using and drink or set aside half of the beer.
Take the beer and the chicken to the grill and push the beer into the cavity of the chicken.
Sit the chicken upright on the grill, making a tripod with the legs and the beer. If you have a secondary rack on the grill, it’s helpful to lean the chicken against that. This may take some gentle finagling.
Close the door to the grill and let this smoke for about 1.5 hours, or until the breast meat comes to 160F.
Remove the chicken from the grill (it’s OK if the beer spills out a bit), and cover with foil.
Let it rest for at least 10 minutes before carving and serving.
If you don’t have anything large enough to fit the chicken, clean out a cooler and use that. Make sure that there is always ice cold water covering the chicken. Also, make sure to sterilize the cooler when finished brining.