As mentioned, he likes the metallic paints and envisions his Orks covered in shiny metal plates, rather than painted up a primary colour like most standard clan schemes. So that was the starting point. I was also a little wary of the orks as i didn't get on with the AoBR Deffkoptas; I just couldn't my head around what I wanted to do with them and the couple I painted are a mess. That said, I think this guy has turned out OK - pictures and comments after the cut.
The big mental breakthrough was the frame style - it's Tin Bitz with a black wash and a Boltgun Metal drybrush, and it looks really, really good. After that I just picked out smaller sub plates and sections in either Dwarf Bronze or Boltgun Metal in a somewhat random fashion to make it look a little ramshackle and Orky. Things like the red fuel tank and the blue-painted plates are done the same way, worn down to the metal with a few extra "scratches" painted on. The main hull is Chainmail with a blue wash and then re-drybrushed with the chainmail to shine it up again.
This is in someways a "quick and dirty" paint job - theres not a lot of complexity and it was done in 10 minute bursts over a couple of days. And it's surprisingly effective.