Free: Contests & Raffles.
Get some orange citrus based food grade degreaser to clean your metal smokers, that's what I used on my master built . But I gifted it to lokidog for a fish smoker, now it's his problem.
I have two smokers. I have an old Little Chief that I use for fish and a MasterBuilt (sic?) for everything else.
I have noticed in my Bradley that fish will leave a little scent. I use a dry brine, let the fish dry out before smoking, and don't use any water in the pan, and leave the vent wide open, so it really reduces the moisture, and makes more salmon jerky, or candy, then smoked salmon. Then when I am done, while everything is still warm, I wipe the smoker out really good with a vinegar soaked rag. Then I crank up the heat as high as it will go and do one 20 minute smoke once it reaches temperature to re-cure the smoker. No more problems.