Browns/Greens for the ork side. Ash, red/blacks for the daemons.
I actually used some vallejo surface primer on some of these (in the airbrush). It worked great. I tried to brush it on...didn't work so well. I was getting sick of the chaos white spray completely cracking everytime I used it.
So ya, going to airbrush my grey and white primers now. :)
I've decided one way to give him decent bulk, is to put him on a flying stand (like a landspeeder). Chop off his legs, green stuff some stormtalon thrusters on the nubs. Stormraven engine and tiny wings on his back...kinda of like a really messed up stormboy. He's been fighting daemons for thousands of years, so I figure he'd be a bit messed up.