most problematic part about doing trains in SE are curves. By doing just a little shortening of the tracks, we may build rails until hinge, build rail over it as if going straight (to enable placement of those tracks) then rotate hinge until rails hit each others hitboxes. Rails should be shortened about as much as to create just about 10-15 degree curves.

Nice bonus would be to create just new rail part, that is one block long, to prevent corrupting old builds and even better to make two new parts, one for each direction left or right, so rails on outer side of curve would be a little closer.