I've been smoke'n briskets for quite awhile now. The best way, imho, is to buy a whole packer brisket, about 12#'s. Don't trim the fat, put on alot of kosher salt and a ton of black pepper. On the smoker fat down to protect the meat, smoker temp 225-300, indirect heat. once the internal temp of the flat hits about 160-165ish it will "stall". I put it in an alum foil pan and cover w/foil(fat down). When the temp gets up to 195ish I'll poke it w/a meat therm to check for tenderness. When it slides in like going into butter, it's done. Pull off smoker, loosen the foil to "tent" and wait at least 30min. I usually wait 30-60min. Separate the point from the flat, slice the flat cross grain and chop the point. Then the point goes back in the smoker to render more fat out and to make burnt ends.
Just how I do it anyway. I've tried many different ways, on a smoker, and this is the best.
The smoker temp can be 300*(I've done a few hot & fast briskets). Same rules apply, just goes quicker and you'll have less smoke flavor. Also remember no two cuts will cook the same, never have for me anyway.