The trouble with the fog in Vue is that it is always a heavy solid mass. Real fog usually drifts in banks and this is very hard to achieve. If you use a plane or a very flat sphere you can usually see the edge of the shape much too well. One could try a terrain with a cloud texture ...

I've seen fog brushes for Photoshop in the RMP, but I don't know how easy it would be to apply them convincingly.