I had a hard start also. I got it figured out.
I make sure I have fuel.  Call for exterior power and air. I make sure all fuel pimps are on I set the bleed switches for the air cond to on, on the flight engineers panel.  On the over head pane,l I set the start switch to low pressure. Each engine ignition I then switch to ground  and by the time I move my view with the mouse down to the throttles it is time to move each fuel lever for each engine up to the start position.  I can see the gauges show pressure and then move the lever to the idle.  It works each time now.
Wayne L Pierce