This sure looks like a quality rig and a quality paint job. I would be tempted to canola oil or original pam the inside only, go with a few smokes and if you see the paint discolor, like at the firebox, hit it with a little canola as it cools. I just keep a can of pam around.
Weber 26.75 OTG w/CI grates & SJ/WSM Mini
Home built 24"x72" reverse flow stick burner trailer with 18"x44" grill w/CI grates and upright SS gas oven/smoker.
Home built 48" fire pit with a 30"x30" Santa Maria style ranch grill.
Home built lump charcoal retort, iGrill & a bunch of other cooking toys.