I had this idea when I was working on my Nurgle marines...
Everyone has these one-pose plague marines from back in the day right?
Well you can turn them into pretty spiffy and fast unit fillers in pre-heresy gaming.
Shave the face grills off, like so.
Then simply fill it out in a mk3 faceplate fashion, also smoothing out the holes in the torso. Remember to also file off the Nurgle icon they have on the groin plate and fill out the cloven feet (almost forgot that one :P).
And there you have it. Clean, fast, easy. :)