In the project there is a scene were the lanscape is black after a fire and to get the idea in the previs video, rather than creating new assets and environment (live and dead trees). I experimented using fog with the camera inside of Maya and it got the effects that were needed for the shot.

To create fast fog in the viewport of the desired camera. Shading> tick Hardware Fog. Usually its quiet white and harsh so to adjust go to the options box next to Hardware Fog and play with the Start and End sliders as well as colour. Its a very simple process and very effective.

Original:

Hardware Fog ticked: 

Further adjustments:

For the final shot I just hid some image planes of the foliage, adjusted the colours of the skydome and the start and end of the fog.