The other day I applied some black wash to them all, the double wall is that stage. Then I applied a mix of stippling and drybrush of Army Painter Angel Green and then VGC Goblin Green for the highlight. Initially I had the side panel highlighted at the top and darker at the bottom but the middle panel was naturally highlighted at the bottom so I switched it as it made more sense. There are still some inconsistencies but it does work better this way.
Far from finished though as you can see the two on the right have has some additional shading. This creates contrast and definition and means the rough drybrush is no bother, particularly with all the texture and the upcoming weathering. There'll be some more black shading to add too for even more contrast and I'll pick out the eagle in Stonewall Grey and White. The reverse is also done but there will be some metallic pieces on there, to match my Bastions.