On the Imperial Fleet, I dry brushed Shadow Grey over the black undercoat certain areas, then, I painted a solid Shadow Grey, like the weapon battery gun decks and the fighter bays. After 20 hours, including breaks, sleeping, and eating, I had finished both fleets.
This last weekend, gearing up for a summer of painting madness, I pulled them out and decided to paint them up quickly. I undercoated them all with black spray paint, and then they sat in my model cabinet, unused, next to my Imperial Guard and Space Marine armies. Then at a local hobby store I bought an Emperor Class battleship for 35% off.
About 5 years ago I ordered the BFG boxed set, and built it up and played some games with the unpainted fleets I had built.