[Licensed to kill]

For the inside, I would spray it down with "Ospho". Ospho is phosphoric acid and with convert the rust from iron oxide to phosphoric oxide which is not only neutral (does not corrode metal) it protects the metal from corrosion. The best way, IMO to stop rust in hard to reach (impossible to reach) places like behind braces. It can be painted over with most paints but it's a good idea to confirm with the manufacturer of the paint you plan to use.