Got these cheap off of eBay with free postage and I'd bought the rulebook late in 2012 at a reduced price again! Score!
Really fun to paint, though the Balewind Vortex was the most challenging part trying to get smooth colour transitions using wet-blending on an un-smooth surface. Probably bit off more than I could chew...
Colours I used were: Incubi Darkness, Kabalite Green, Syrabite Green and White Scar. I put them all into my colour palette and deliberately left a space between each so that I could mix a 'mid' colour between each so that the blend was even. Finally, I washed it down with a mix if Coelia Nightshade and Lahmian Medium. I think the green was a good choice as I toyed with the same Aqua Balefire colour and also a yellow to red "flame" transition but I think this looks more eerie and magical.
I also trice another new technique on the rocky skulls: sponging! I wanted a granite type effect and am really happy with the overall effect. Initially, I basecoated with Adeptus Battlegrey then followed this with the sponge technique, hitting the recessed areas with Skavenblight Dinge. Then I chose Karak Stone and used a "leopard spot" technique in the more raised areas or in place adjacent the previous sponge layer. Then I used Rakarth Flesh in a similar way, targeting raised areas. It was a bit light at this stage, so I then used Codex Grey to sponge around and over some brighter areas. I washed the whole skull section with Agrax Earthshade + Lahmian Medium. Using the hair dryer to speed up the drying process, I then used Nuln Oil to add more depth to the cracks and inside the skull eyes and nose. I repeated this on the eye/nose area to really make them stand out.
Also I spent ages painting the step areas in three separate base colours: Charadon Granite, Adeptus Battlegrey and Adeptus + Chaos Black (1:1). I then highlighted up with Stormvetmin Fur and then Codex Grey, followed by a wash of Nuln Oil.