As already mentioned, grind the inside with a wire wheel down to bare metal. Then just run a few foodless cooks with a hot fire to season the inside. Spray with cooking oil before hand and let cook for 3-4 hours. Repeat 2 or 3 times and you oughta be good.
18" OTS, 22" OTG, SJ Silver, Cimarron Offset, Coleman Bullet, PBC, UDS, QMaster ATC