Suck it and see
Black & Decker’s Dustbuster is very handy. It needs to be left on charge when not in use, and if used with powdery materials, the filter will need frequent cleaning.
My weapon of choice for clean-up jobs on the layout is this brush attachment to the hose of the household vacuum cleaner. It has a soft brush and plenty of suction.
A cheap battery-operated mini-vacuum that I bought off ebay. I’m thinking of exchanging it for something more useful... like a chocolate teapot.
Thanks to the local housefly problem, I find that my track needs vacuuming a couple of times a year. Occasionally this may lead to the need for localised re-ballasting.