studio shoot question for nice bokeh

I did number of shoots but never able to take creamy bokah shots... realize if I want to shoots @ f1.8 or 2.0 with my 50mm I get too much light since strobes are getting into the picture....for best shot I have to use f5.6 & 1/180 shutter...

Same problem I faced when shooting in daylight and backgroud was sky, i always have to shoot with F5.6 + to have proper sky exposure (using flash for removing shadows) which means I wont be gettting good bokeh....

I think I am missing something basic...can somebody suggest....(i am thinking of buying ND filter, but will that help in studio portraits?)