Its a close guarded secret!! Just kidding!! Here is a recipe we've used for our home cooks thats similiar to our competition brisket. For comps we inject beef flavor back into the brisket. I feel that extremely long cooks (in a dry smoke environment) remove a lot of the natural beef flavor. We normally inject our brisket with a beef injection for competitions.
Rinse about a 13 pound brisket under cold water. Lay it in a disposable aluminum pan and spray with a 50/50 mixture of Jack Daniels and Apple Juice. You do want some moisture on it so your rub will adhere to the meat. I put on my rub, liberally!!!! The amount of rub you use is up to you. Remember, the amount of rub does have an effect on the amount of bark that it will produce. Smoke them fat cap down for the best Bark.
I do not trim the fat cap. Trim it AFTER it is smoked. That's where all the flavor is.
If you leave the fat cap on, you will probably not need to add a Beer. There is going to be PLENTY of juice in the bottom of the pan. But, a little beer is not a bad thing. Just lay the meat in the bottom of the pan.
Smoke it at 225-250
NOTE: sometimes the meat will get to an internal temp of between 140-160 and just seem to stay there for hours. It happens. It will start going up again.
When it gets to about 160, cover it with foil (pan and all). Make sure you have some juices in the pan when you cover it. If you want that bark to crisp up, uncover it at 190 internal and let it cook to 195-200.
Pull it off at 195 and let it rest for a couple of hours
Use an internal thermometer probe and smoke it to 195-200 internal.
This can take anywhere from 8-12 hours depending on the size of the Brisket and the cooking temp.
Do not be as concerned about the smoking TIME as you are about the internal meat temperature!