I've just finished off this Death Eagle... He was originally meant to be painted green and become part of my Salamanders army but in the end I decided to paint him in the black and white Death Eagle colours. I have two chaplains to paint for my main marine army so I decided to use this model as a way to learn how to paint black armour.
Here's a step by step for the black armour. Firstly, the model is undercoated black as you might expect...
Notes for Rogue Trader Nerds:
This mini dates back to about 1989 and was scuplted by Mark Copplestone. Here's a Stuff of Legends page showing it in that year's Citadel catalogue. What I didn't realise when I started this little project is that these aren't the original Death Eagle colours. Similar to the Salamanders, they had totally different colours back in the day which have been replaced by a much less unusual scheme now. Here's the original scheme (picture from the Death Eagles page on Lexicanum)