Painting Rusty Armour

How rusty are we talking?
For heavy rust, start with brown (bestial brown for instance) then dabb on slightly dilluted vermin brown, then finally blazing orange. Apply it a bit irregular. Do not apply it as highlights, you want the orange in the crevasses (since thats where the water will stick -> thats where the most severe rust will be). Drybrush lightly with chainmail. Wash with browns if you want it to look dull.

I'd say go quite easy on the orange and the chainmail drybrush, but its all a matter of taste.

Unfortunatly I just got some basing shots with this technique, with varying rustyness.

For some not too heavy rust effects:
Over a black undercoat, drybrush 1:1 mithril silver/scorched brown. Then highlight with mithril silver. Then paint a bit of water down bestial brown on areas you want rusty. Wipe off any excess bubonic brown.

It's quick and easy, and I did it on my SH bases for great effect.

Thanks alot you guys! thats really helped.