How do you build railways in realistic without babysitting trains?

I have trains in my game running on 2 tracks (traffic staying to the right) and I have found it almost impossible to expand my network or replace track in this game on realistic. How do you all do it? If I have to lay track, the track layer ultimately has to reverse direction to come back home and gets denied by my semaphores unless I babysit them or create short track to let them briefly reverse and cross over to the other track to put them back facing the right direction. And replacing track with electrified track? Freaking nightmare because all the trains using that track now have no way to get anywhere because you all of a sudden have no route if they're diesel. I don't know. Is there just some trick to doing track in realistic?