Here's a really good painting video tutorial for the Death Guard "How to paint Death Guard Chaos Space Marine by Lester Bursley": http://www.youtube.com/watch?v=DpyoxsJ1UoQ I hope that helps you out. He make some fantastic videos.
Good luck, stay frosty
This one doesn't use airbrush. It does use the old GW paint names though.I'd be interested in seeing one that doesn't involve an airbrush (as I don't own one). Even if it wasn't a video but a blog post with photos...
I've been working on my death guard for a little while now and the "grungey, eroded" feel I'm going for isn't translating well. It just looks like a sloppy paint job.