All painted from scratch in Photoshop. Took ages to dab in all the gas. I used a default soft round brush and set areas of gas to different layer modes.
This image is a personal project, so doesn't belong to anyone else, i.e. a client. The full rights to this image is £30 ($50).
This image took several days to complete.
To create a similar finalized image would cost about £320 ($500).