I also had this problem this summer, though it was just some surface rust. I have an insert painted a matte black finish, Jotul Rockland to be exact. This insert also comes in an enamel finish which would protect much better, but i like the flat paint. They sell stove polishes, but most say they are for unpainted surfaces. I emailed jotul, and the reply was to paint the stove every other year. Wow, thanks for the advice. Nothing i would like better to do than move my 500 lb stove or tape off my living room. I bought this stove because of its flush face looks, so i didnt want to have any rust showing, even a little.
Anyway, my solution. Because it was just minor surface rust, i wiped it down with some WD-40 on the cosmetic faces. It made the surface rust disappear, and should leave a thin protectant film till the burning season starts. Its not heavy enough to leave a film that will burn, and WD-40 doesnt harm paint. Ive also seen people suggest putting a bucket of damp rid in or around the stove.