A: For cleaning Lionel trains, use a soft-bristle toothbrush, a mild dishwashing detergent, warm running water, and a wide sink. Also, make sure to have plenty of light so you can see what you’re doing.
Start by taking the plastic shells and parts off the chassis and accessory frames. If removing parts is too difficult, clean some surfaces on the accessories. As long as the decals aren’t flaking I don’t worry about them; the only paint that’s really sensitive is silver.
Wet the dirty areas, put liquid detergent to the toothbrush, and gently scrub an area with no lettering. Rinse off the soap and check your progress. If the place you’ve just cleaned looks good, continue to scrub everything while rinsing frequently. Set the shell on a cloth towel to dry. I use another soft towel to remove excess water.
Clean die-cast locomotive shells in the same way. The plastic parts on switches can be cleaned with Armor All, a soft toothbrush, and a clean soft cloth. Clean track on switches with either a fine wire brush on a bench grinder or a fine abrasive like a Walthers’ Bright Boy. Heavily corroded track is rarely worth the effort to clean, so I suggest replacing it.