I agree with Bob about the paper. Wet burlap or foil work great.
Wild sage is pretty strong, I use it when cooking outside. IMO it doesn't take much.
You've already cooked this way so you probably know to use hard wood and get the hot coal deep enough to last through the whole cook.
Not sure if this is of any help but here are some underground cooks I've done.
Sometimes I soak pintos overnight, put them in the pit with stock, onions, garlic, peppers, seasonings and let them cook along with the meat.
Throw a turkey in the pit too...they come out delicious! :)