pretty simple, first I toss it on the grill and heat it up, 250-300 ish, then use a verity of wire wheels and roto strippers. Keep it hot while working it. I work on the lid awhile then wiped it out with a wet paper towel and swapped it with the pot on the grill. repeat until your happy with it. make sure you get all the dust out. and pop it back on the grill and dry it thoroughly. I like a solid shortening, Crisco or something similar. Coat all sides and place back on the grill up side down, crank up the heat a bit, 350 ish and cook an hour, then turn the heat off. leave the lid closed and let it cool slowly. When its just warm to the touch apply a second coat and repeat the heat and cooling process.
This is just how I was taught, Ive never played with it to see what was necessary and what is not but I like the results.