Great stuff and airbrush work! I have found these vids really informative for weathering : http://www.youtube.com/user/OrcPainterNerd
true, they are good. (and I was the evil who scanned the first one in, the second was by someone else)but if you've got some cash to burn, both Forgeworld's Model Masterclass books are absolutely brilliant. Take the first one if you can only afford one, or dig through google if you can afford none. ^^
But really, they're treasure troves, those books.