Are your locos showing poor running qualities?
They probably have dirty wheels.
 
These T-shaped Stainless Steel Wire Brushes are superb for cleaning dirty locomotive wheels to help improve electrical contact with the track that will help improve the running qualities.
 
 
Works with Dremel or slow speed drills
Shank Diameter: 3.2 mm
Stainless steel wire bristles
Includes two brushes per package
Does not cause after-rust when used on corrosive-resistant materials
Ideal for locomotive wheel cleaning
Very effective on flat surfaces and in hard-to-reach places, such as slots
Great for cleaning, deburring and surface-finishing items made from stainless steel, aluminium, silver, pewter, or other white metals such as DJH Kits.