Your chimney should be wide open.
Take the sand out from under the firegrate or raise the grate up with something - rock, 1/2 bricks, etc. Open your vents - full open to start and then down to 1/2 or smaller as the chamber comes up to temp. Don't close the chimney damper except as a last resort to snuff a fire down.
" Edited since I seem to be the only person that has zero success with the Minion method in a sheet metal horizontal." Do it their way and then make a simple bakset and see if my way just might work. :D
Extend the chimney down to the cooking grate with a split juice can or a piece of aluminum flashing formed into a roll.
If your wood is nice and dry you can use it to supplement the charcoal or burn all wood - however, an all wood brn takes a lot of attention.
Basically it sound like you're not getting air flow and may just have too small of a fire.[/b]
Southern Brethren BBQ Competition Team
"It's all about getting paid!" - Myron Mixon
"I love being hated in my hometown!" - David Hair
KingFisher Gator Rotisserie cooker, WSM, Stainless 5 burner with IR gas grill, Turkey Fryer, Weber JD Commemorative grill, slightly used Bandera chamber for future use as a cold smoker, Masterbuilt 40" insulated ELECTRIC smoker