Beside "painting" with a flashlight at night using a still picture camera and tripod for long exposures to give either a flood or spot effect, the flashlight, especially if it has variable output, can be used as a shadow fill light under bright light conditions. The fill light would be used if the contrast range from bright to dark is more than the lighting ratio a camera (film or digital) can handle. A flash either on or off the camera can also be used. A reflector with either metal or white board can also be used as a fill light with the advantage that the fill light will never overpower the main light. It is best to use a spotmeter to view light ratios.
Using the light as a fill light might look a little unusual if the tint of the light was way off the tint of the main light.
Using a flashlight to paint at night it is best to keep the light moving around at a consistent speed and area unless you are going for a spot effect. And, of course, do not point the beam of light at the camera. You'll get one or more weird trails of streaking bright orbs on the picture doing that.