Get your smoker going and set to 250 degrees. The key to smoking is low heat, long time. This is what breaks down the connective tissue in tough meat, like brisket, and makes it awesome. You need to be able to maintain a constant temperature through the entire process. Electronic smokers are great at maintaining the constant temperature. Old-fashioned ones just need more supervision. As far as what wood to use, I like hickory with a little mesquite. But you can use any hard wood you want, cherry, apple, alder, and even a little oak. And there can never be enough smoke. The more the better!
Do not trim the fat on the brisket, you can always remove it at the end. It is what helps keep the brisket moist. The salt seems like too much, but it is going to create a crust on the outside only, and lots of it will fall/melt off while in the smoker. Season the meat with the rosemary first then the salt and pepper.
Place in smoker, Fat side up, for 3 ½ hours. Then flip it over for 4 hours. You will know it’s done if you grab a corner of the meat and pull up and it tears away from the rest. This where you will want to remove the fat. I wear thick rubber gloves (because is it HOT!) and use my hands. If everything works out just right, you will be able to just scrape it off with your fingers.
There are 2 pieces, a top and bottom, it is ok to separate them, since there is some fat and connective tissue n the middle. Once fat is removed, Cut against the grain, serve and enjoy!