If the fire is clean and hot you don't need smoke, but we will add it here anyway. Make a new layer just under the fire. Select a very dark, almost black, airbrush and paint in some smoke. Create another blank layer above the smoke but under the fire and set it to "screen" mode. Using a soft medium orange airbrush add highlights and color to the bottom parts of the smoke billows where they might recieve light from the fire. Change the brush clolor to medium red and add more color just above the orange areas.