The interior is all stainless steel. Ensure all foil has been removed and if you can scrape up heavy stuff with a plastic putty knife. Steel is good if you don't mind scratches. Warm up the smoker; then turn off and make sure unit is not plugged in. Easy Off oven cleaner on entire interior. Try not to get much on the heat element but it should not hurt. Wait a 15 to 30 minutes or so and with a a nylon scrubby pad or plastic putty knife, and a bucket of water, start cleaning. Rinse, repeat as necessary (No need to heat a second time after the heavy stuff is off). After cleaning, a solution of white vinegar diluted in warm water should remove oven cleaner residue. Treat the exterior similarly. Then season with wood as per instructions.