The person who told you to run the press with gray balance was the right person. The press is fairly simple. 4-colors, white paper, good light, and a consistant ink density in gray balance. You will have the best target you can get. I recommend you pull 50 sheets when the press is “up to speed” and select 10 random sheets. Allow them to dry and read each target. Average the target findings and create your profile.
You will then “dumb down” the inkjet proofer to print just like the press.
Good proofing software will handle the ICC exchange. Watch your inkjet ink densities. They can go way over the presses’ densities and screw everything up.