Where in El Paso are you located? First off, looks like you want to do this "barbacoa" style. You could definitely do a brisket this way, but keep in mind it's A LOT of work for a single brisket.
Couple of things I'd suggest. Do not use wet newspaper. It will break down, make a mess and not to mention you will get that ink all over the brisket. Use foil instead. LOTS of layers of heavy duty foil. You will want to season the brisket and add some type of liquid to it as well. Since it is wrapped in foil, the only thing you will benefit from by cooking it under ground, is the heat. The smoke flavor, sage etc will not give it any flavor cause of the foil barrier.
Now, you can add sage, bay leaves etc inside of the foil. After you wrap in foil you can use wet burlap sacks on the outside and then use bailing wire to keep it in tact and to help remove it when it's done. Many people also use agave leaves or cactus leaves (pencas) as a barrier between the coals and the meat. These are loaded with water so they will keep the chamber moist as well, but remember that the foil layer keeps all that stuff out.
As for the bbq sauce, I wouldn't know how to do that unless you put everything in a pot, or Dutch Oven and then let it sit and cook in the hole as well.
It can be as easy as dig a hole and cover it, most times folks around here have lined the inside of the hole with rock or brick.
You are basically using an oven technique. I am familiar with the wild sage you are talking about, but I couldn't tell you if it's a good idea to use it one the meat itself versus just using in on the coals for the aromatic smoke.
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