To the OP,
What's the reason to smoke without a brine or rub?
A question just for clarification. You're going to smoke and eat immediately, right?
I would NEVER smoke or cook any fish without using cure#1... Recently, botulism has become somewhat more prevalent... Smoking and/or cooking will not reach a temperature that will kill the bacteria and still render the meat delicious.. Salt and cure#1 will allow you to have delicious meat...
All that being said, I'm just an old fart that is still enjoying life...
Even this corona virus has an up side.... I have NOT received one ROBO call in a long time.... The local "door knocking" church group hasn't been around.... Taxes have been put off until June or July... I got my new mail box installed.... Someone drove over it and didn't leave a note...
I stopped bringing my salmon years ago. Just season it right before it goes on the smoker uncovered. I keep my seasoning simple cuase salmon doesn't need much.
If I understand, you want to smoke salmon without cure or preservative, immediately eat majority of it and finish the rest within the next 3 days. I'm assuming you will still season with salt and pepper (maybe a little lemon juice, onion and dill).
I think as long as you cook to 140 deg and hold it there for a few min, the salmon would be safe 3 days later IF you immediately chill to 34 deg and keep it at 34 deg until consumed within that time frame.