I was using a metal trashcan wrapped in fiber glass insulation with a crock pot as a dual heater/humidifier. It was very easy to control. Basically I set the desired temp and filled up the pot every few days. I found placing the probe roughly in the middle of the kiln where the leaves were hanging was best. There was condensing humidity on the sides of the kiln, but I drilled a hole in the trashcan to let it leak out. My only regret was not purchasing a larger crock pot - not for heating power, but to reduce the number of times I need to refill the reservoir. I’m sure the edges of the kiln were cooler since that’s where humidity was condensing, but that was fine for me since there was no tobacco there anyway. If you were to build a larger kiln, it might not be a bad idea to put a small fan in there to try and equalize the temperature. Then again, if you have good insulation it’s probably not a big deal.
IIRC, I simply plugged the crockpot into the “on” outlet of the controller. The “off” or work 2 outlet would be used if you had some sort of active cooling mechanism, but that’s overkill for a tobacco kiln.
I’ll be following this as I need to build a larger kiln soon!