Questor, First, BBQ is not done in an oven, Second, never score the meat before cooking, and never remove the fat before cooking.
You can do a fair job on a brisket in the oven, Use your rub,, them place it on a roasting rack in a roaster large enough to take the entire piece of meat. Place it on the rack with the FAT side up, turn the oven to about 350 for an hour or so to brown the meat, then cover loosly with foil or with the lid to the roaster, allowing two inches or so above the brisket, reduce the heat to 175-200 degrees and let her cook for 3-4 hours. Remove from the oven, remove the lid or foil and let the meat rest for an hour before attempting to slice it. After resting, remove as much fat as possible without cutting into the meat, slice across the grain and serve with the sauce of your choice. (When I don't make my own sauce, I use Masterpiece..........it is very good!)
Most briskets will have grain running at more than one angle, you may stary cutting across the grain and later find that you are cutting with the grain. When you do simply change your cutting angle.
Good brisket should be tender to the point that a knife is not needed to cut it, but should remain togeather when sliced. Keep in mind, the best brisket always starts on a grill or smoker. You can brown one on a smoker or grill to get the smoled flavor, then move it to an oven to finish the cooking at 175-200 degrees for 2-3 hours.
I did 10 briskets and about a hundred pounds of ribs last week for a club function. I used the mesquite and the wood from a pear tree that I had removed from my yard. It turned out great, a good mesquiter flavor, but not too strong. I kept one large side of ribs for the wife and I, they were delicious, but after three days I was ready for a change.