Cheap products used on most Chiminea's that will not allow this to hold paint.
The only thing that most people dealing in Chim will agree upon is that the best way to protect the clay part of the chim is to periodically coat the outer lining of the chim with liquid floor wax. This seals the clay and keeps water from getting inside the pot or skin.
I do this periodically and it also adds some deep coloring to the thing. Love to burn Pinion wood in these things, smells so good.