I've received several compliments on my tutorial, you could try it if you like:
https://drive.google.com/file/d/1fqV8jQFhyR6D7BhlvdyH4F6JJjvLVmSM/view?usp=drive_link
Note that in JOSM, when you paste the rails to a new layer, use CTRL-ALT-V instead of CTRL-V, this will place the rails exactly...