To get him looking like that I would:
+ prime/undercoat him white
+ do a nice thin coat of Karak Stone (or some other light tan/brown colour) over the armour sections that will be greeny brown
+ do a thin wash with bel-tan green wash over the bits painted above
+ do a thin wash of nuln oil, using a wet, clean brush to clean the black wash off the flat surfaces and concentrate it in the recesses of the armour - use a clean dry brush (or tissue) to suck up any excess black wash/water as it pools
+ when dry do a thin wash of agrax earthshade wash over the top of the green
+ Paint the metal bits with ironbreaker (or another mid darkness silver colour), then lightly wash with nuln oil when dry
+ Paint the bone bits with the bone coloured paint, then wash fairly heavily (or several times) with alternating washes of earthshade and sepia
The rest you should probably be able to figure out quite easily. If you want any more suggestions though, just ask.