I'm not painting genius by any stretch of the imagination, but I sure can recognize painting genius when other people do it! Further, why bother going through the process of explaining to you what other folks have already done MUCH better than I could have? Am I right?
With that in mind, I present to you two articles on weathering by Aaron "Grey_Death" P. over at The Painting Corps. Aaron does some fantastic work, and most of his techniques are incredibly simple to implement (his Medusa army in particular is just stunning...). At the moment I'm attempting to apply some of the techniques below to some scenery projects I have on my own hobby table. Once that's perfected... maybe I'll give this a shot on my models as well!
Weathering Armor: Link to Article
Deceptively simple, yet amazing results. A "must see" tutorial.
Weathering Marines: Link to Article
Like the armor article, this uses a very simple sponge technique that anyone can do.
As you can see, Aaron is pretty talented, and he's willing to share his talent with all of us. We should take him up on the offer. Visit his site regularly and catch his regular weekly tips... you won't be disappointed.