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I do know some mural artists who use a professional grade air-gun to spray the sealer on, but this requires better knowledge of the workings of an air-gun than most people have.
Make sure that colors match up evenly at the seams before pasting the mural. If the mural is smaller than the total wall space, mark out the dimensions lightly in pencil on the wall. Determine where to begin hanging your mural and which panel to start with. Some murals come with recommendations of which panel to start with.