Thanks for the advice Rick. I also thought that if it was running, there would be no white on the engine cover due to the heat, but I decided that I'd make it look as though it had been left overnight and had got a layer of frost all over. Would the rubber on the wheels frost if left long enough?
Actually, on re-reading your post, I see what you mean. The white isn't meant to be camo, it's a normal green Cromwell thats frosted.