We used to have to park the buses at night by reversing into a narrow gap. A couple of inches between mirrors was all the room you had. It is actually easier to reverse a long vehicle than a short one.
I really learned how to reverse on mirrors, later, when I was a van driver in the motor trade. I would deliver to a dealer and perhaps had a 200 yard drive though tightly parked, pre-registered, cars to get to the stores entrance. It was then necessary to reverse back out, with only inches to spare, between all these brand new, expensive motors. As long as there was daylight between your van and the surrounding cars you were okay. Secret was knowing where your rear wheels were. Obviously you had to check that no one had driven in behind you, but you did that before getting in the cab.
Now the only practise I get is reversing into my garage, where I have to place the car tight against one wall so that I can get the driver's door open sufficiently to get my large frame out! Jazz is a bit easier than the Volvo was!!