I worked out a good scheme with a
gw store employee, but didn't write it down. I'm currently trying to 'rediscover' it.
What I can tell you is that the base consisted of retributor armour, followed by seraphim sepia in the armour grooves.
The next steps are what I'm hazy on, but I think it went like this:
Layer 50/50 retributor armour and liberator gold.
Line highlight with pure liberator gold.
Sparing picked out highlights with runefang steel
Fortunately I have some old marines from when I started out in
40k so I have plenty of rest subjects. Pardon the obvious sloppiness.