You can SHIFT + LEFT CLICK on any upgrade icon in the industry tab to upgrade ALL factories near worker limit.
Do this once or twice a year and you should not have any problems.
Alternatively, CTRL + LEFT CLICK upgrades all factories of the type you just clicked on.
Do this once or twice a year and you should not have any problems.
Alternatively, CTRL + LEFT CLICK upgrades all factories of the type you just clicked on.