Coat salmon with a generous amount of the brine mixture and allow to rest, skin side down in a plastic or glass container (large resealable bag works well) for at least 12 hours or overnight in the refrigerator.
Depending on the size of the salmon side or fillet, 2-4 hours will be required for smoking. Therefore, 4 hours before serving, remove salmon from brine, run under cool water to rinse off residual brine mixture and pat dry. Place skin side down on wire racks and set out in an open space (out of direct sunlight) to dry. Circulating air really helps here, as the objective is to allow a thin whitish layer, "the pellicle" to form. This will take 2 - 3 hours.
Meanwhile, prepare the Keg for indirect grilling at 200°F, fill the diffuser with water and add wood chips.
Maintain a constant temperature of 200°F and smoke the salmon for 2 1/2 hours, until the flesh is firm to the touch, opaque and flakey.