weathering powders?

Cheech,

If you get the pastels in chalk form, make sure you are getting pastel chalk and not the pastels that are like crayons.

Dave

I've been told the Mig pigment powders are excellent, because they're just pigment. A pastel chalk stick has a carrier to keep it in stick form. This (allegedly) interferes with the way is can be applied. Personally I have no problems what-so-ever with pastel chalks, but I am considering picking up some of the mig pigments to see what they're like.

There's an article on pigment/pastels on missing-lynx.com:
http://www.missing-lynx.com/reviews/other/migpigments_skubik.html

I've seen them at the LHS for several bucks, they just look like pre-ground pastels to me though. I think you'd be better off hitting a Hobby Lobby or similar store and picking up a 4 dollar pack of pastels and using that.

You'd use the airbrush to paint the model and the pastels to apply weathering effects, not one or the other, but both to compliment each other.