@trainroomgary has put out a useful video on the subject:
For a trolley or other line with sharp curves, I recommend using an 1867 or 1877 short flatcar with the truss rods removed; cut slots in the magic eraser and slide it over the truss posts to hold it in place. Use an 0-4-0 switcher to push or pull it. Don't forget to add weight to the flatcar!
Mitch