For the 10% that I shoot that may need a flash I just use a couple of cheap remote units with Vivitar 285 flashes and those positioned low/behind and up bounced out of white (not silver) umbrellas to fill. I use a dark background behind most models. When we built our house, I purposely faced the front windows to gather northern light so on those days when the light coming is strong enough I ditch the flashes. I find that the overhead light in my studio/living room is just enough that all I need is a touch of fill from bellow to even out the tonal range.