When I was a "cookie boy" at a YMCA camp (long ago) we used the same technique to make cinnamon toast for 200 campers - except we didn't have the cool rack.
We would toast the bread on the baking sheets, then butter the toast with a 4" paint brush dipped in melted butter. Then we would flip the whole sheet into another pan with cinnamon sugar and pick them out by hand. Stack them 5 high (10 people at a table) and into the warmer until the breakfast bell rang.
I wonder why I gained so much weight that summer?