For low and slow think pellet smoker. Any decent pellet smoker with digital control should run in the 165° F neighborhood on its lowest setting.
You can add a cold smoke chamber to get the temp down even further, or just use one of the stainless steel mesh containers to burn the pellets
and leave the main burner shut down, then after you get enough smoke on them finish off in the dehydrator. Far as that goes any kettle type
charcoal grille would serve the purpose if you just make fire in a smoke tube gizmo. Go on amazon and search for "smoke tube for pellet grille".

I did some blue cat nuggets that way last summer and they turned out real nice.

If you have a salt slab you might try using that and see how you like it. I did some catfish on the slab and it turned out too salty, but with the
trout still having the skin on, it might be just about right.