Not know which Brinkman smoker you have, I can tell you what I did. I have a Brinkman Trailmaster. I used some dryer ducting to lower the exit point for the smoke. I wrapped half fire bricks with foil and lined the bottom. I got a welding blanket ( Harbor Freight ) and fit it all around the main tube. I then used heat bubble wrap around the outside, even the chimmey. I also found a thin wire basket that fits in the firebox. I got it at Bed Bath and Beyound in the bathroom section. I can cook a hot and fast brisket at 325 to 350 even in the dead of winter.
Lang Wide Body 84 Deluxe Modified & Brinkman Trailmaster offset