I thought I would share a technique I am using to clean brass plates and brass journals. The brass identification plate on my new old switch tower was tarnished, rusty and hard to read. Sorry, I didn't take a closer picture of the before.
I removed the plate and cleaned it. See how it turned out!
The "Lionel" was not even readable before. To clean this, I started with some old Tarnex I had around on a paper towel. This didn't do much on its own, but it is an important start. Then, I sprayed the plate with WD40 and used a Scotchbride pad to lightly work the dirt loose. The WD40 loosens the tarnish that the Tarnex activated. (I'm making this up. I have no idea why it works.) I don't use much pressure. I was afraid the black lettering would come off, but it is all still there. I alternate the steps until the plate is clean. Then I wipe it off an reinstall it.
This works with nickel journals too, but for those I use fine steel wool.