Another +1 for the water and dawn dish soap clean out. After that season it. Rub the inside down with cooking cooking oil then start a basket of charcoal. Let it dry cook with the intakes wide open. After that's done, your second cook should be a-ok.
18.5" OTS, 22.5" OTG, CB Silver(Rip), Vintage Coleman Bullet, Pit Barrel, UDS