69 Dart Dash - Painting Back Side

The back side of my dash looks like it has never been painted......bare metal with some light rust here and there. It would be a real pain to try to sand it. Can I just apply some kind of primer to the bare metal and then apply acrylic enamel? I could just ignore it, but it seems a shame to re-install it with bare metal in there. Comments and recommendations would be appreciated........james