YouTube can be fantastic for these things. Last time I was clueless about modern mechanisms like Ultegra gear changers and how the cable threaded though. Previously I'd only changed them out in mountain bikes which are totally different but also a complete bu66er especially the sram ones. This time a quick bit of youtubeing showed me exactly how and where to get to the cable nipple

so instead of being the hardest part of the job like last time, this time it was the easiest. I reckon a straight bit of wire would be good for threading through the frame. The thread and superglue worked well for me this time though.
They all work pretty much the same way ever since the indexed down tube changer.
The all have a drum with hole that the cable nipple locks in and a ratchet type system for the indexing so you just have to work out where the drum hole lines up with the cable insertion hole, easier said than done sometimes, or like on MTB shifters you have to remove an access plate.
With brifters the ratcheting mechanism is very delicate and quite complex and best left well, particularly with Shimano, and all of the access is hidden under the hood.
To some degree the new electronic wireless systems are the most simple and with some work BSim could even change gear for you.
I expect that will be one of the next upgrades they make, well ahead of actually making the simulator 'simulate'.