Yes, cherry pickers for me as well. I am also always impressed with keeping scale and perspective on such large scale pieces @tattoodjay I figure they must have it on a grid on paper for reference and then they can make it larger, much as you do from a small sketch or other refrence piece onto a larger canvas.
In the future there will be machines, almost like 3d printers, that will slide down the building depositing paint as it goes laying out a mural in one swoop, like a giant printer.
NOt being artistic at all and cannot even draw a straightener well I really do not know much about art, but I guess many do just s you say draw a sketch or plan with a grid and use that to guide them i Think your right about the 3D machines to print murals, but I kind of do not look forward to that too be honest seeing the artist at work makes the murals more impressive to me