thesteelclaw asked about painting rust. Since it's a topic that's separate from the new paints it can have its own topic.
The way I paint rusty metal is not to rust it too much. As I briefly mention in the painting section for the Slugga Boys then I just use watered down armour wash with watered down chestnut wash in places once it has dried. The armour wash takes the shine off the weapons and leaves them looking used while the chestnut wash adds some patches of rust and fluid leakage. The same effect can be seen more liberally used on my Killa Kan (although that's my first Kan, so it's a bit rougher than the newer one)
I never measure the amounts, but I'd guess that I normally do about one part ink to two or three parts water with the rust mix. With it being ink rather than paint I then soak up as much as possible and apply it wherever seems reasonable. If it gets a bit too waterlogged then dry the brush and remove some of the wash and re-apply it elsewhere.