Not sure if such a thing still exists but there was once a product made by 3M called "Color Key" Color Key was made in pre press where each of the 4 colors were separated into their own sheet of a clear acetate. You then would overlay and register one sheet of acetate over another sheet, to arrive at a "progressive" viewing of a 4/c process job. These sheets of acetate were best overlayed onto the exact sheet of paper that the job would print on. There were even provisions that could be made for dot gain so that the simulation was reasonably accurate. Far better results that the Hail Mary method of just waiting and seeing what youve got after the final pass. I would suggest making some inquiries with the company that sells you your pre press supplies as even if 3M no longer makes it another company may have kept it alive.