I have gotten advice from some of the more experienced Lang users on this forum to treat the rust with grease. Knock off the rust, rub in some no name Crisco shortening and cook a while. I don't know the value of doing it this early on a new smoker. Maybe once you see a bit of rust would be a good time to do it. I'd hate to tell you to make a sticky mess this early in the season if it doesn't cure properly. Get a couple of good smokes under your belt then one day when you are finishing up a smoke and you still have a good fire going rub down a section and see what happens. Let it cure on there just like you did with the inside. I am treating my firebox that way and it seems to work out pretty well. This isn't a one time thing, I'd just hate to have you do it this early, if you do have paint problems like excessive rust I'd hate to be Ben Lang with the phone call. Hey Ben, my smoker is rusting like crazy, yea what happened, some guy on the forum told me to rub it down with Crisco. That idiot, if you had a paint problem I could fix it, but with all that darn grease on it, to bad!
Let me get you a couple of names to pm if they don't respond to the thread.