I hit my stuff on shelves once a month with a feather duster. Does almost no good. Don't really care. Really, you (and by "you", I mean "I") shouldn't have any more stuff than will fit on your layout, plus 25% shelf overflow.
Embrace the dust, become one with the dust, and may the dust be with you.
"Cleaning" a scenicked layout is kind of like going out and "cleaning" the front yard. The shiny toy layouts may be different; don't know.