Bounce Cards and Reflectors
You don't need a truckload of lights to illuminate your scene. A common and easy solution for shedding more light on your subject is to use a bounce card or reflector. These are either pieces of cardboard, cloth, or wood that are colored white, gray, or silver to reflect light into shadowy areas. You can buy inexpensive flexible reflectors that twist into a compact circle for storage. You could also create your own reflectors—white poster board covered with aluminum foil on one side, for example.
Have someone hold the reflector, or mount it on something, and aim its reflection as you would with a fill light.