I'd love to jump right in and start writing Selenium tests but this is more of a manual situation because adding tests would be a whole thing that I don't have time for. Is there a way to manually interact with one browser (IE) and as you do things the commands are copied to other browsers (Edge, Chrome) so you can see in real time how a website behaves in three browsers without having to write any code?
Perhaps it would be a hacktastic Selenium IDE solution? Perhaps it would be an OS level thing where you mirror mouse and keyboard events to each monitor? Perhaps it could be done with a VM?