opnspaces,
Thanks for the question. Charcoal formulas seem to have started in Utah.
Cooking with wood is hundreds of years old. Dutch Ovens were carried by Lewis and Clark, fur trappers and the people coming across in wagons after the Gold Rush. They cooked with wood and sometimes buffalo chips.
There are no formulas. You learn quickly with some practice. I can heat up an oven by eye to 350 degrees. You can test by holding your hand near it. The tendency at first is too much heat. You have to learn it. Trust your oven. Shovel coals over and under and be patient. I never run out of wood in a forest. I have lived my wall tent for a month at a time and never run out of wood.