Shooting in a dark room. Camera on a tripod, exposure time in M mode, from 1 to 30 seconds. If this is not enough, we shoot in BULB mode, pressed the shutter, pressed the shutter. The exposure can be from 1 to 10 minutes. The light brush is a flashlight and a set of removable, color filters with a diameter for a flashlight: white, blue, green, yellow, orange, red. You can use one flashlight and replaceable nozzles of colored filters made of black thick cardboard rolled into a cylinder. You can buy 6 flashlights and make them with different colors, it is more convenient, you do not need to change the filter to a flashlight in the dark, but you must put a black cylinder on the flashlights, it hides the light from the flashlight when working. You can work without a cardboard cylinder, then when highlighting objects in the photo, illuminated objects and a color filter from a flashlight will be visible, it can leave a beautiful color pattern, but this is for luck, as luck would have it, it can turn out well or badly.
I used a mixed light, a flashlight and a pulse. A flash with a color filter or the reflected light of a flash from a colored piece of cloth. paper for filling the frame with a color gradient or without a color filter reflected from a white or silver reflector towards the frame.
You can choose flashlights of different diameters for different tasks. For small objects, small flashlights, for large ones, large flashlights.