Depending on how much of your scenery is actually attached to the baseboard, whether buildings or ballast,etc., you could try using a re-chargeable vacuum cleaner. With the motor of these not being too powerful, they may just be ideal. If you have the likes of loose ballast, then use a small brush as already suggested, with the cleaner a short distance away to collect just the main dust. Following on from the cleaning, could you not use some old bed-sheets as dust covers?