I use a custom build track cleaning locomotive build by R. Kleinsteuber ( Dutch LGB trains : Website
www.dejachtkamer.com choose menu: Locomotieven spoor-G) that has a rotating brush at the front and a vibrating minitool sand paper machine in the middle of the two drives.
I can lift the sandpaper when it is not necessary to used.
Normally i run the cleaner without the sandpaper machine each morning after rain in order to swipe of all the sand particles.(my track is at ground level.
When not having used the track for a long period i have to use the brush and the sand papermachine in two rounds along my track.
I case of heavy corroded track, that occurs most time under trees or concentrated rain drop off points, i use a abrasive sponge from FESTOOL mounted on a flat pad on a long stick.
The sponge info: 98 x 120 x 13 mm ; two sided ; Festool Granat 220 ; No 201114.
Two swipes with this sponge, wet or dry, will do the heavy corrosion job.
Gerard