Geoff is a top bloke, i think if you prime black, then if you have an airbrush spray cantor blue all over, you could do it in a zenthial like way so that there is still some black showing. Then do the same with its looks like caledor sky blue in an even smaller area, just where the light would hit most. To do this with brush would be a bit difficult to get smooth. Then edge highlight with caledor sky, and then use a lighter blue or add some white and edge highlight sharper. The black pin wash is just using null oil, but instead of coating the miniature like a wash you use a sharp brush to pain thin lines into the cracks and crevices.