Pork Butts and Picnics are relatively Easy .....Briskets are NOT! I'm Still trying to Master Brisket but I'm getting better.
99% of the time if a Brisket Flat is Dry it's Undercooked. If you cook/smoke a Brisket, Rest It and Find the Point Good but the Flat/ Slices Dry and it did not crumble on you then continue slicing - put slices is oven pan - add beef broth and put it in the oven at 250-275 * for 1-2 hrs and enjoy the point while the flat/ slices finish. You can do the same with whole flat instead of slices but it make take 2-3-4 hrs. You can do it the next day if need be.
I've done it with Brisket and Round Roasts that were tough or Dry-- the round Roast I sliced and added Beef Broth and 1/2 Jar of Spicy Brown Mustard and ran it for 2 hrs at 250* and it was Tender and Delicious!
Dry Brisket can also be chopped for Chili Meat or similar too.