What are safe, effective practices for smoking salmon in a commercial 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.