Small necro reply I guess.
I haven't shopped a game in about 11 years. Before this, my tools of choice were a wirewheel on a bench grinder, #0 Steel Wool, Toothbrush, Ivory Dish Soap, and water.
I would use the wire wheel for EVERYTHING metal. If I couldn't make it perfectly shine, I considered it old age on the game. Sitting down for hours cleaning metal posts, plastic posts with a toothbrush, and soapy water.
So I was just thrown for a loop with "how in the hell do I get rid of this crap on this lockdown bar receiver?". I got rid of my wirewheel when I moved and got married. I just got an ultrasonic cleaner, and a rotary tumbler, and OOMMGG, what a difference. For the receiver, I just used a scotchbrite attachment for a dremel, and some 320 grit sandpaper to try to scuff it up a bit for painting. My thought process was always "I will try to make metal things look brand new, but if there are a few scratches, or small discoloration on it, I think it makes the game look vintage." I never liked BRIGHT WHITE paint, SHINY SHINY CHROME, and things like that on pinball machines. I grew up in the 70s-80s era, and things got damaged, and as long as the game worked great, I didn't care.
So I try to clean, but not obnoxiously so. Don't get me wrong, HEP restored, and Herb restored games look beautiful, but they just aren't my cup of tea in my gameroom.
Quoting the pipe, I made a 36in long 4in diameter PVC tube. I put vinegar in it, throw my pinball legs in there, and wait 24-48 hours or so. (This is not scientific by any means). I can then bring the legs into the shower, rinse them off and use some #0 steel wool to get rid of the crusty stuff on them (it just falls right off), and it's pretty amazing. I cleaned quite a few about 8 years ago, and haven't unpacked the legs yet. I'll post a response to see if they've rusted up again.