Driver training schools for 18 wheelers as well as RV 5th wheel trailers offer several videos on YouTube that offer good advice for backing trailers. They offer right and left side, straight in backing as well as right and left parallel parking. After watching those videos, went to a parking lot and practiced each technique. Now after several years I still remember those techniques and have used all of them at various times and situation. Some of which were deemed near impossible by others. Of course it takes a fair amount of searching in YouTube, but they are available.
BTY I was a prime mover driver in the Army that had to back in howitzers for fire missions and I can assure you that 5th wheel trailers require different experience. All it takes to gain confidence is the proper technique training and practice.