What would be the best way to paint ork skin?

[Sanguine Syn]

The goblin green and the wash is a pretty good idea..i tried it on a few of my boyz and it looked pretty good..if you want a Darker color try Dark Angels green.  

[Rev.Matt]

Start black, paint orkhide shade, do a layer of 1 part orkhide shade 1 part snot green, another layer of snot green and finish with a thraka green wash.

You can highlight again after this with snot green and even an extreme highlight of 70/30 snot green/ bleached bone.

For even better results blend more layers of orkhide shade through to snot green.