It starts with a metal basecoat with a couple of fine layers of coloured glaze over the top. Add in the now ubiquitous heavy weathering and you can get a mini that looks pretty awesome.
Heres a few of the photos i've come across so far (all pilfered from Heresy 30k):
I think it does look particularly good for Alpha Legion, but i could see it being really good for Ultramarines, Emperors children, maybe Night Lords. Could it even work for Blood Angels? Might end up looking a bit pink.
Im really quite tempted to try this out, but considering as most of my Emperors Children base colour work is already done, the only contender might be my future loyalist Raven Guard force (and i'm not sure this technique would look quite as good doing solid black armour)
What do you guys think?