I bought a very nice 5.5 pound brisket flat from a local butcher. I put some mustard on the meat to get the rub to stick better. The rub was mostly paprika but included onion and garlic powder and salt. I used my new Masterbuilt propane smoker but did not have a good thermometer. The door thermometer read about 10 degrees colder than the boiling water. I kept the smoker between 225 and 250 for about 4 hours until the internal temp was 180-185. It had no bark. The rub was mushy. I could taste the mustard and it was not a good taste. Very disappointing as the meat was expensive and I had guests. What should I try next that might be easier and what should I do next time for better results?