Painting and weathering PE razor wire for modern military? How do you do it?... thanks!

I guess it really depends on what condition (tied to a vehicle, in use, etc) and what AOR you're working on.

I used matchsticks cut to size and painted with Vallejo Red Brown for the fence posts on this vignette. The wire is Verlinden P/E barbed wire, painted red brown and then scuffed lightly with a medium grit sanding stick. The shadows are a bit bad, but you might get an idea.