These kans were really easy to paint. I started with black primer, then painted them a chainmail/boltgun colour. I let this dry overnight. The models were then washed with a combination of black and chestnut for a murky brown, with matte medium added to help it settle into the crevices. When that was dry I added some more browns in a fairly random fashion, though aiming for the bits that would be most rusty. Finally I added some MIG rust pigments for extra rusty bits. Then I drybrushed with the base metal colour, to bring the metal back a little. When all that was dry I applied a coat of matte varnish and left them to dry overnight.
The next stage I sprayed the models with some cheap hairspray. As soon as it was tacky dry I painted the panels and armour casings in yellow and black, a few white bits too. Then I used a scruffy old brush dipped in water to scrub and pick at the paint. The water lifts off some of the hairspray, leaving a chipped paint effect behind. Some very worn bits I might touch up again - it depends on how the scratches turn out, it is quite a random technique. I then used a diluted army painter strong tone to give some contrast and depth, a sort of blacklining for cheats. Finally for this step I glued them on the bases then gave them a coat of matte varnish to remove the shine from the hairspray.
The final stage involves painting any extra details, mostly pipes, plus more shading and lining where needed. I also added black brown on the exhaust pipes, gun muzzles and thinned it to make an oily wash to apply around rivets, leaking from random points. Finally I painted up the simple bases, the usual drybrushing on the rocks and a bit of washing with paints and pigments on the sand. Job done, ready for gaming, let's hope they don't get blown up in turn one.