M. Brindos
Another effect that I like, besides steel and aluminum dry brushing, is painting the surfaces NATO Black and rubbing them with a graphite pencil. The effect has has a perfect sheen of rubbed steel.
You don't even have to use black as a base color. I've used a graphite pencil for all sorts of fresh/bare metal finishes such as hatch rims and warn contact areas on hulls and turrets. Works especially well for machine guns.
Test it out and see for yourself.
Oh, and if you still have any laying around, an old no.2 lead pencil will give a darker iron look. Easy effects to use and look realistic without much effort.