I think at that point it's almost better to come with paper printouts for 2 reasons. 1: Tacticale/shareable/paintable in a physical meeting 2: It drives home

I think at that point it's almost better to come with paper printouts for 2 reasons. 1: Tacticale/shareable/paintable in a physical meeting 2: It drives home that it's a sketch, with bad customers a visible UI so easily hides the enormous amounts of complexity that can sometimes be under a "simple" UI and make it hard to educate them as to why the UI sketch one did in an hour or two then needs 1500 hours of engineering to become a functioning system.