Assemble 3 or 4 sections of straight track, place in a convenient spot, preferably not on a light color carpet. Spray 2 or more pieces of paper towel with plastic safe contact cleaner (or any other solvent you trust) and place it over the track. Push the cars back and forth by hand. Even the dirtiest wheels are clean in less than 10 seconds. Entire trains of cars can be cleaned in minutes this way.
You can do this on the layout depending on how it is detailed. My weathering and roadbed detailing is not something I want to continually subject to solvents so I use the separate off-layout track sections.
