I tried to get this orc done in an hour, after undercoating. I didn't quite manage it, but that was entirely down to drying time for the wash of Agrax Earthshade that I slopped over him at an early stage. Drybrushing and contrast paints did the rest.
This fellow's destined for some Pulp Alley and Galactic Heroes games as a primitive member of a batch of orkish desperadoes. But he's also a test piece for one of several Hordes of the Things army I want to throw together from various odds and ends that my son and I have lying around.
Using Hordes of the Things with 40K miniatures may not be the most obvious thing (although it has been done a fair bit before), but we love the game, and it seems like the best way of using up a lot of otherwise redundant plastic.
There's also a bit of fun to be had in building each element. And the sheer size of the 40K miniatures means that each base will hold only a couple of miniatures. I reckon a full 24AP ork army will probably involve around 20 minis in total.
I've started off by converting some Warhammer orcs into orks, chiefly through left-hand (and gun) transplants.
Meanwhile, space marines will form blade elements, with marine bikers as either riders or knights. Imperial guards might be hordes - or perhaps shooters or spears, if equipped with las-cannons. Genestealers and tyranids might get in on the act too, as beasts and hordes, respectively. Once all the 'scraps' are used up, I might allow myself the odd eBay purchase to add some more exotic elements - as long as it can all be done on the cheap.