I built some very quick and cheap smoke marker, started yesterday evening and finished today.
The green smoke looks a bit darker than it does in reality - I´ll try to take some better pics on friday during our test game, maybe I need to touch it up a little with lighter green.
-Form the basic cloud shape out of tin foil, glue it to the base
-Mix acrylic caulk with water and baking soda, let it bubble up a bit as the soda reacts with water and apply to the tin foil.
-Let it dry thorougly
-Paint it up in the color you like (I used my airbrush to enhance the subtle color changes in the cloud - best seen on the blue smoke)
In the background, the next bits of terrain - more rocks in the making!