Any suggestions on weathering the flight suit?
Seeing as it's already black, you may want to weather it with some grey or graphite coloured paint. Easiest way to do that is to get the spraypaint, lay your suit out somewhere (outside, preferably) and mist over the suit. So don't spray at it, allow the paint to fall on the suit. Using spraypaint will ensure that the weathering stays when you wash your jumpsuit.
Also, depending on how beat up you want your suit to look, you can get a 5 gallon bucket, throw the suit in, throw in some rocks and gravel, seal it up with a lid and roll it down the sidewalk/street/hill a few times or 3. Then take it out, give it a good shake and see what you've got.