For this i would really recommend using the Bokeh function in fotoshop from the NIK Collection (analog efex pro2).
DOF in daz is ok but setting up the proper camera settings can indeed be hell.
I don't really need it, not any longer anyway. I have learned how grayscale depthmapping works, from my Poser era, and, now, I simply use the gradient tool, and soft brushes, along some gaussian blur on masked selections, to fix a proper alpha/depth map for the lens blur photoshop filter, moving from the focus circle and outwards