Until now, I have painted the helmets of the Dragon figures. A lot of material dealing with German helmets can be found on the web, these helmets will be painted in slate grey.
I started with priming with Tamiya medium grey and then hand painted the helmets using Vallejo Black Grey with some Russian Uniform added to lighten the color.
Inspired by an example from Calvin Tan (http://zyclyon.blogspot.ch/2011/09/alla-prima-wet-on-wet-with-acrylic.htm), but he is using acrylic color with drying retarder) I added tiny spots of different oils (yellow ochre, burnt umber, black, warm grey) and blended them carefully with a brush dampened with turpentine. You have to work very concentrated and stop blending in time, otherwise the helmet is covered with a single color mix. First, I tried also using blue, but this can result in some ugly greenish tint together with the yellow and orange tones.
When dried, a point wash around the rivets was added. Then, some highlights on the top of the helmets were added using the Vallejo base color lightened with Deck Tan.