I may be doing it wrong..
I just use the temperature control that is on the oven with an oven thermometer (kitchen type) to monitor it. My oven also has a timer.

I set the temperature for around 350 F and the timer for 15 minutes. Place the boards in the cold oven. When the timer goes off I leave the board in the oven with the door closed. The slow cool down seems to have less oxidation than a fast cool down.