I learned a few tricks myself when I was doing an X-Wing helmet and I was working on the set of Green Lantern last year as prop/costume flight gear consultant. I was able to get some great tips from one the paint guys on set. He had been doing that stuff for like 20+ years! He was amazing he could make paint look like rust and you had to be less than 10-12" from it to tell. Step back 3 feet and it looked like rust it was insane!