I ALWAYS use a wet brine with fish, except for when I make Indian Candy.
12 hours absolute minimum, 24 about right, 36 is going long but I have done it. I NEVER rinse the brine off the fillets and I NEVER pat them dry. I put the fillets (usually, chunks of fillets), skin side down, on the smoker racks that I sprayed first with Pam
I was just typing away and a bunch of what I was typing disappeared, what the hell???????
As I was saying, the racks are laid out on newspaper to catch the drips. Leave them to air dry at room temperature, (Pellicle forms in about an hour.) then into the smoker.
Don't think I ever put apple juice in a fish brine but it should work just fine. You did not need that much sugar, and if you also added syrup they are going to be some sweet fish.
The "standard" brine for fish is a gallon of cold water, a cup of sugar, and a cup of salt. I generally, but not always, add soya sauce, garlic and lemon juice.
Brian, you have my e-addy if ever you have a question about smoking with the Luhr-Jensen smoker............
Doug