My 16x19 feet layout is in an L-shaped addition to our house, with a window AC for temp control. I regularly change the filter in the AC unit for dust control. Not a perfect solution, but a canister vacuum cleaner with a dust brush attachment on its flexible hose is too clumsy and powerful for the job -- it sucks up scenery, scale figures, etc. Even the classic DUSTBUSTER device is too much suction.
I've seen (but never bought) a battery-powered mini vacuum unit intended for cleaning a PC keyboard and crevices -- small but perhaps effective on a train layout.
Mike Mottler (ritrainguy)