Do my post processing in Photoshop Camera Raw Editor. Then convert to Grayscale and open the image in Photoshop. Change mode from Grayscale to Duotone. From the Duotone Option window at Presets choose a Duotone, Tritone or Quadtone that you like from the drop down menu. Change mode from Duotone to RGB Color. That's what I use for most of my black and white's.