I'm almost positive that your 0-4-0 switcher is a Varney judging from the valve assembly and more importantly the drawbar. As for cleaning up the brushes and contacts, pick up a can of "electical parts cleaner" used for degriming electonics. I get mine at Home Depot and it works great. Best part is that you only have to remove the shell, but it does require you to re-lube the engine. Have fun
Sean
Sean