The side-light should illumine the smoke enough to allow your camera’s autofocus function to focus on the smoke.
A camera setting of aperture of f-8 to f-10 at ISO 200 can work reasonably well. Make sure that camera is completely still. You may use a tripod stand or a firm rest with a timer setting or a cable release. Keep the auto-focus point a the centre of the thick portion of the smoke,
Experiment a bit with a digital camera to keep the best shots while rejecting the bad ones.
The inset picture shows the improvised set-up on a chair with black background and a photograph of the smoke lighted up an LED torch.