I use the Tichy Group Fire Excapes as well. Nice product, reasonable price.
I prime them, then paint them flat black. After drying, I "mist" them with with combinations of Tuscan, Red Lead and Roof Brown to get a rusty kind of look. You can also apply small amount of Baking Soda in areas where you want to give the appearance of deteriorating rust and paint over it. After applying those misted coats, I give it a little more flat black.
You want to streak some rust color down the side of the building where the supports are anchored in to the wall.
If you're going for a real run down, dilapidated look you can apply a flame to the under side causing the plastic to slightly bend. Got to be careful to get it just out of reach of the flame so it because pliable, but doesn't collapse.
