Pat dry the salmon with a paper towel and place on a rack lined sheet pan.
dry brine: In a bowl, mix together the brown sugar and kosher salt. Lightly coat the skin side (about ¼ the amount of the brine). Thoroughly coat the meat side of the salmon with the rest of the brine. Place the salmon back onto the rack, skin side down, making sure that it’s lifted from the bottom of the sheet pan. Cover with foil.
Let sit in the fridge for 8 hours or overnight to marinate.
Rinse off the brine with water and pat dry. Place the salmon back onto the rack uncovered.
pellicle forming: Place back in the fridge for at least 5 hours or until it forms the pellicle. The skin should be tacky and glossy. Remove the fish from the fridge and place it on the counter for about 30 minutes to prepare for even cooking.
Preheat the smoker to 140-150 °F. Add the fish and close the lid. Using low heat to prevent overcooking (forming albumin, or white spots) until internal temperature reaches 130~140 °F
Let the fish rest on the counter, uncovered for about 10-15 minutes.