We have been smoking salmon in an electric smoker (a Master Built) for about 6 months now, using a dry rub brine recipe containing salt, brown sugar, garlic and other flavorings (sometimes brandy, sometimes smoked red pepper powder). We have tried to adjust the temperature and time to gain a safe, but moist and smoky tasting end result. We have been using mesquite wood chips. I have read that the authentic way to smoke meat is very slow over a smoky fire and can last longer than what is possible in a commercial smoker. How can I achieve the best results with my smoker?
I am projecting here, perhaps, but I think the question you're asking is "why doesn't my salmon come out moist and succulent like what I get at the store?"
A couple reasons.
First: you want to properly cure the salmon for at least 24 hours beforehand. 36 is better. To cure, you will need two whole sides of salmon (or one cut in half), with the skin on. Rub your cure into the flesh--so 2:1 salt:sugar, plus whatever other spices you care to use. The addition of brandy sounds lovely; I like tequila or a nice peaty/smoky Scotch myself, or maple syrup (but obviously nix the sugar if you're doing that). Place the two pieces together, flesh to flesh, optionally including herbs between. Wrap very tightly in plastic, completely sealed, bung into your fridge to let it cure.
Second: when the fish is cured, remove from the wrap, rinse off the cure.
Third: time to smoke. If you want dry and flaky, hot smoke--this seems to be what you're doing and what you don't like. Therefore, it's cold smoke time. The two basic ways to do this are either to add LOTS of trays of ice to the smoker itself, or to route the smoke through a cooler filled with ice and then back into your smoking chamber. A quick Google should provide you with diagrams for doing so.
Do not over-smoke. Fish picks up flavours quite readily, and will dry out if oversmoked, even if cold. Really for salmon I don't think you need much more than 20 minutes of cold smoke.
I think you are cooking your salmon for too long. When I hot smoke salmon, I'll do a 1 1/2 lbs salmon fillet at 180F to 200F for about 35 - 45 minutes. Depending on the size of the fish you may need shorter or longer. This is sufficient to get a nice smokey flavor and properly cook the fish. Cooking for hours will make the fish very dry. It sounds like your only real issue is the length of time you are cooking it for.
This assumes that you are smoking the salmon to serve and not as a preservation method to keep for a long period of time. I don't know how long this method will preserve the salmon, but my guess is no longer than normal cooking methods.
Of course, you may still prefer cold smoked, the end product is quite different. But I don't think it's time to write off hot smoked yet.
There is no need to cold smoke to get juicy salmon. The trick is to properly dry it after brining overnight. I put the salmon in my fish dryer till it has a nice pellicle forms, then it's ready for smoking.