I do this whole evolution once a month.
I blow dust off it with compressed air: as mentioned above this redistributes it, however I have a Dayton powered HEPA air filter in the trainroom that runs all the time and sucks up alot of that and I use a shop vac on the whole layout every so often.
Using compressed air tends to loosen and redistribute small bits of "vegetation" which makes cleaning the track more important than ever, since I have had bits fall between the rails and jam the gears on at least one engine (WBB Trainmaster - took forever to free it). The photos below show my "comprehensive track cleaning train"(The CTCT Special ) in which I try to do everything in one train.
The loco is the first I bought when I got back into O scale - an RTR SD70. A good loco that can pull this heavy load.
First up: the magnet car: just two very powerful neodymium magnets taped to a plastic flat car. Picks up the odd screw or whatever that might be down between the rails. It always comes back with something it found, even though there should be nothing there.
Track cleaning car, from Pat's Trains if I remember correctly. I usually run it with a dry pad. This does an excellent job but loose fibers wear off the pad and wrap themselves around the axle trailing it quickly, creating additional friction.
Probably redundant given the cleaned car above, I run this homemade one I had before I bought the other: just a box with a lever and weigh inside pushing a Brightboy track cleaning eraser down on the tracks.
Finally, cleaning up after everything is my vacuum cleaner car, which I've posted about in the past. Guts of a Dustbuster. Originally I had a 10-amp full wave recitifer and it picked up power from the track. But it wants 8.5 to 9 amps at around 14 volts to spin up properly which runs the train to fast to vacuum well, and 9 amps leaves too little out the 10 amp circuit breaker maximum for the loco. Now I run it with two 18 V B&D rechargable tool batteries as shown. One of them will run it for about five minutes - enough to make enough passes to clean half my layout: then I turn the car around and use the other battery on the other half.
Edit: you reminded me, I always do this whole evolution on the first of the month. Close enough today - I will do it this afternoon.