I'm happy to admit that I got it wrong first time out and had to repaint. The mistake I made was painting them as people; I started them as grey and started layering up to white like I did with the organic shapes of Gandalf the White. What I should have done was treat them like objects, exactly the same as if I were painting a tank or something else.
In the event, the final process was this:
Thinned down black wash as a line wash.
Black for undersuit.
|wash thinned with wash medium and carefully lined/slathered all over|
|Flat panels repainted white|
One major thing I did was a bit of cutting and shutting. I am a touch irritated that FFG are shipping a premium priced product with single, duplicate poses. I'll take that for a Blood Bowl team or Necromunda gang, but not in a Big Box game like this. So the trusty jeweler's saw came out and various arms and waists were re-positioned so every member of the squad was unique.
Trying to decide now whether to do the Rebels next or complete the Imperial side by doing the speeder bikes - but before I do that I have something rather big to deal with...