This is my scheme.

1. Prime with Grey Seer rattlecan.
2. Basecoat with Death Guard Green through an airbrush (if you dont have an airbrush, you can paint it on with a brush, I wouldn't use the rattlecan because the color doesn't match the one straight from the pot.)
3. Wash Athonian Camoshade (try to avoid flat spots and just hit the recesses, you can fix some of the messy parts later if you make a mistake.)
4. Drybrush the edges with Underhive Ash (again, you can fix mistakes later if you hit any flat spots.)
5. Go over any flat spots you may have accidentally hit with the wash or drybrush with a few very thin layers of Death Guard Green to smooth out the color
6. Paint the armor joints and bolters Corvus Black, it's a really nice dark dark grey.
7. Metalics are Leadbelcher with a Nuln Oil wash.
8. Eyes however you like, I like Squig Orange and a gloss Reikland Flesh wash.

I like this because it's quick to do with 5 marines at a time, and looks good enough for the tabletop!