This is my current favoured formula for very weathered/aged/battle damaged Imperial Knight miniatures. It’ll work on vehicles like tanks or armoured miniatures like Space Marines as well, but it’s probably easiest on the scale of a tank or Knight!
I undercoated with Vallejo Mecha Primer in black, then base coated the silver section with Citadel Iron Hands Steel. The blue was Citadel Thousand Sons Blue. I used thinned paints to build up a smooth and solid colour.
Next comes Citadel Rhinox Hide on a sponge (actually a torn out piece of a pick ‘n pluck-style miniature storage case) applied along any raised edges and across the center of any broad surfaces.
After that, I heavily stippled Citadel Mournfang Brown in smaller areas than the Rhinox hide, generally staying within the Rhinox Hide-covered areas. After that, a lighter stippling of Citadel Evil Sunz Scarlet and Citadel Zandri Dust added in a couple more variations on the rusted look. I’m on the fence as to whether Evil Sunz is too bright or not – the next time I’m going to try something a touch darker to try and make the red pop less.
A heavy wash of Citadel Agrax Earthshade really took the brightness out of the colours and made the Knight look like he’d been fighting for some time on an acid-rain world.
For the chassis beneath, I used the same technique but did a heavy drybrush of Citadel Ironbreaker after the Agrax Earthshade wash to differentiate the frame from the carapace.
After the drybrush I did a light drybrush of Citadel Ryza Rust on select areas such as below the eye lenses.
More in progress shots next time!