This is a photo of oo gauge train wheel cleaner and 009 narrow gauge for trains the same size as oo but with narrower track for trains and narrow gauge trains. The black ones are for really dirty wheels and the white is used after to make it super clean. 

This is all in a sliding drawer and is suitable for both analog and digital systems. I used kitchen runners only costing £3. The wires are soldered  onto brass screws straight from the track.  It clips on and off with crocodile clips.