Im sure with the variety of tracks, plastic and wood there are different methods used.
So I'll star with the one i use on my wood track.
It is a Swiffer handle , swiffwr attached pf course, and an old Mercedes body on an Artin chassis pulling it around. The swiffwr handle has a hole in it, which is ecured to the trunk with a large head screw. This allows the swiffer nearlt 180 degrees of float.
I usually run 2 slow laps so the swiffwr cleans each lane, then follow with 2 or 3 medium laps where the swiffer slides to the sides and the gutters. Its amazinf at what it collects, any debris in the slot is kicked up by the cars guide and gathered in by the swiffer.
Here is a couple of pics. Lets see what everyone else uses.



Bob