Sorry, didn't read close enough. That was my UDS. Let's change gears...On my double barrel smoker, one of the barrels still had a coating of light oil in it. I stoked the bottom barrel with wood and let it go. I wish I had a pic, it smoked up the whole neighborhood. I thought someone was going to call the fire department. Anyway, it burned off really good and then I scrubbed it down with some steel wool and really rough sandpaper. Then I washed it out and coated it with some vegetable oil and burned it again with a slower burn.
Forgot to add the barrels were already assembled when I picked mine up. They were already double stacked and welded together by two pipes between them.
Another thought, if you have a propane fish cooker, put the barrel on top of it and fill it with some water. Start it up and when it gets hot, start scrubbing!