I am using a ceramic kiln as I type for powdercoating.
I originally set this kiln up for heat treating metal. I have yet to experiment with it for that but it is a natural for powdercoating. It is capable of holding temps to 2400 degrees.
Old ceramic kilns can be pretty cheap. You will want to look at the coils as old kilns often need replacement coils. It is not hard to replace them and they are not that expensive.
To control the circuit, I use a microprocessor circuit...which you could do too i you have any aptitude to electronics.
First I am not using a core microprocessor but a package system which is fairly basic in operation. I have been using what is called an OOPIC but they fell off the face of the earth over night. A very common replacement would be an Arduino.
I don't know if this is in the scope of what you can or want to do but it is how I approached it.
In the programing I pick climb rate fast or slow, peak temp, hold time. I am going to modify it to use two peak and hold times.
I have a 55g drum I am experimenting with. I put the part in the drum and spray it. I am thinking of a low volume fan/filter in the side to keep the airflow going through.
Pick my temp, pick my time, drop in the part.
It is real easy for assembly because I can turn on the kiln, sand blast a part, clean it, coat it, fire it and within an hour or so be putting the part back on the car.