I have been studying pictures of black armour, both real life and digital renditions, to give me some ideas how to tackle this area. Translated to painting, I first stippled black all over the dark brown basecoat. I have left the brush in the photo, it's just an old one that is no longer good for fine painting, but is still useful for mixing, drybrushing and stippling. I then mixed some khaki into the black to give a dark grey, stippling this on the upper edges of the armour and anywhere I wanted more light. Next, I added some light grey into this mix and stippled towards the edges only. Finally, I applied thinned light grey (with a standard fine brush) to the very edges and around any dints or scratches. There was a tiny bit of light grey paint left on my palette so I quickly picked out the horns. There's still work to do on the black armour, but I need to paint the metals first to see how they contrast with each other.