These were great fun to make, I used a combination of a Titan weapon, the gun from a 40k Space Marine and two Tracktor Kannons to customize these. To paint them I undercoated them in Chaos Black then painted them with a 50/50 mix of Tin Bitz and Brazen Brass all over. After that I dry brushed them with Boltgun Metal until they looked appropriately like rusty metal. The other bits are just Chaos Black and a thin coat of Blood Red.