I smoke steelhead mostly and use to smoke lots of salmon. I use a cup of salt to a gallon of water for the brine. It's soaked for 12 hours then rinsed.
The steelhead gets gutted and headed. And cut into 3 pieces.
I smoke at 180°F for 10-12 hours making sure I never go above 180°.
Anything higher and you risk cooking not smoking