>>6617344If you're going to use foam be sure to seal it and then prime and sand before you spray.
I suggest using a variety of colors when you use spray paint. I like the hammered metal spray paints when doing metal armor pieces best, especially when the armor needs to look really worn. Using a couple of different colors really makes it seem more real imo. As for dents/cracks/slices, I would suggest making them before you paint, then embellishing them after. Scuffs can be made after you paint. Mad jelly you have an airbrush, you can do quite a bit with that!
The wonderflex tutorial
>>6617298 posted has a pretty good painting/weathering walk through. It also includes a "how to" to make real rust weathering (which is pretty easy). I can't really tell from the art, but it looks like there's rust on the boots so maybe that might be useful to you. Good luck and please post in the progress threads!