This is the kind of thing I really enjoy doing. One simply finds the middle of the wall, top to bottom and side to side, draws a plumb line, and away we go. Starting from the middle, and then going both directions, allows for equal expansion on both ends, and if the stretchy soft paper begins to bend, it does have far to go before you reach the end of the mural. One has to be able to work from the left or the right. (ambidextrous)
The mom was more excited than the kid. The kid only wanted to play with new musical potty designed to help him get rid of diapers, which in this case would be a good thing because the child dropped a lot of "stuff" from his diaper running around our work area.
When I mentioned that I enjoyed doing this kind of thing, I meant hanging the mural, not walking in poop. Just to make that clear.