I've got twenty pounds or so of silver salmon I got this past summer that I want to smoke. I've got an electric smoke, but I've never smoked fish.
Good fish needs nothing beyond brown sugar and non-iodized salt, 2:1. There is absolutely no point in adding nitrates and nitrites to your food...
Salmon fillets cut in chunks, for silvers about 6 pieces per fillet works best for my set-up, but it is completely non-critical. Try to keep them all about the same size, though.
A food grade 5-gallon plastic bucket works well for brining. I usually boil about a gallon of water and dissolve the brown sugar and salt in it to create a hypertonic solution. After boiling it gets poured into about a gallon of cold water in the brine bucket. I let this cool further while preparing the fish.
Brine for about 90 minutes, stirring at least several times during the soak. Rinse VERY quickly under cold running water and arrange on smoker racks. Allow to dry until a good pellicle forms which should be dry to the touch and look a little glassy.
Use lots of smoke to start and keep the temperature way down... Salmon smoking should NEVER exceed 140F, especially with silvers and kings. The oils will break through the pellicle and denature to ugly white blobs. Kings and silvers are the hardest to control because kings are super oily and silvers are very wet fish.
Smoke does not need to be continuous, but heat must be fairly consistent. Smoke for an hour or two is plenty and it is easy to smoke too much.
Wood makes a big difference in taste and using blends of different woods is usually better... Alder is a favorite local wood here, but lots of fruit woods, mesquite, black cherry, hickory, and maple add a lot especially in small doses.