I'm assuming by business portrait, you mean a business head or bust shot. I do lots of that sort of thing, and I use a very simple, almost foolproof system. I have a speedlight inside a 30" Lastolite Ezybox 30 degrees camera left (or right) and my 30x60 Lastolite diffusion panel close in on the opposite side to add a bit of fill. Find a blank wall, have the client 3-6 away and that's really all there is to it.
I would NOT try and use continuous lighting for something like this; even if you're packing around Kino Flos it's going to be a challenge, and I DEFINITELY would not use an on-camera speedlight under any circumstanace. NOTHING screams "amateur" more loudly than on-camera flash catchlights and red-eye. Since you've already got the soft-box (and I assume) a light stand, then D-I-Y some way to use it with your speedlight (Remember, Gaffer's tape is your friend) and if you don't already have some, grab a set of Yongnuo or Cactus radio triggers for $<50. Done.