Bearcarver - I think your edited notes on brine time is spot on at 4-6 hours max to impart the desired brine flavor and affect without making too salty. Then rinsing very well with cold water and pat dry with paper towels before air drying. Forming this critical pellicle so filets are fully dry to the touch is really important to me. I do this on the same type of racks in a cool dry basement on top of the wife's washer/dryer with a couple small fans circulating air across them.
My brine recipe is as follows ( my friends and family won't let me mess with it - I agree):
1 Quart Water
2/3 Cup Kosher Salt
1/3 Cup Morton's Smoked Sugar Cure
1/3 Cup Light Brown Sugar
1/3 Cup White Sugar
2 Tblsp Maple Syrup
2 Tblsp BBQ Dry Rub
2 Tblsp Smoked Black Pepper
1 Tblsp Lime Juice
1 Tblsp Dill (or to taste)
Combine all to boil, simmer 10 minutes, remove from heat & add 1 Quart ice then stir. Rest/refridgerate.
I cold smoke the fish to a 140+ internal temperature ( I only have store bought fish available to me). Note my favorite is Steelhead trout as full filets. If I use larger filets of Salmon, I slice in half lengthwise and remove the small bones along this line by simply slicing on either side of them when splitting the filet ( just like "zippering" the Y-Bones out of big walleye filets before frying - don't smoke as there isn't enough fat/oil like there is in salmon - I tried/failed once).
I use a pair of mailboxes on top of my smoker exhaust and can easily hold the mailbox temps constant at 120-130F. Note, I like to smoke a couple of pork butts below at 250F at the same time using charcoal and some apple wood smoke. I used to use one mailbox, but was forced to fabricate a Y-Adaptor using home duct work fittings riveted together and use two mailboxes to double my output to 5-6 pounds at a time. It goes fast. Attached are pictures.