I usually use a track cleaner from www.schienenreiniger.de Sorry their website is only in german.
I've got the small hand cleaner, and their cleanig fluid. These stuff saved us during the Intermodellbau 2009.
I also use simple wood blocks for track cleaning, especially after painting tracks, but also between the operation.
It won't harm the rail surface and is quite effective.
Sometimes I use a track rubber.
Markus