How I approached the painting: undercoated using a gray spray paint. I then used green and brown washes for the skin and clothes. Various metallics were applied to weapons, helmets, buckles and the like and spots of base colours like reds and blues. I put some more spots of wash around some details and then finished of with the lightest of light green dry brushing on the Ork's skin only - my previous dry brushing was a bit overboard so I restrained myself. The basing was just kitty litter and some basic washes and then I sealed the lot with a matt varnish.
The whole job took about a week of evenings (which seems like a lot in retrospec) but no complaints, it was good fun.