First of all ; the people need understand the "Know why?" and the "know how?" of VSM.
For psychology reasons the human understand the current situation better if the current situation is very well depict (charting the flow of information, process and materials) in front of them , therefore if we want understand where are the 3M (Mura , Muri and Muda) in our process, the idea to create a diagram that show us this opportunities is very well accepted. The must important thing as I have mentioned is to see, Waste , Overburdening , Variation and identify the gap between the Present and Future State.
Gemba walk , yes we must walk the process end to end , or door to door , charting the flows ( 3 flows Material , Process and Information), take pictures , draw by hand , and put together. Event that in many books the VSM is represented in just one page don't be naive the process is not short , small and as you thing. Be prepare to walk and walk.
Here one video that shows how large the VSM can be.