One thing that can make things even more difficult is if you have a pump not large enough to maintain pressure, or with large line losses.
When this happens every valve adjustment affects all the others.
Lets face it. Most of the time we make a educated guess on the settings.
A plant with a competent operator is always better off than those who contract out all their work. No manager wants to pay the bill for a service person to tweak valves and check temperatures when he sees nothing changing.