Marvel mystery oil & a bit of WD on a rag works real good for me,, going over the pipe with the rag, & then immediately following up with fine steel wool or ultra fine Scotch brite.
Might have to repeat the process a few times....
Don't recommend circular motions with the steel wool/ Scotch brite ect.,, just back & fourth, with not to much pressure,, as you will get swirl marks ect. in the metal.
The 3 stage Pipe on My GX-200 turned out real good in doing this,, & the bluing transition on it is really cool looking,, & it's shiny.
Added,,
Just wiping the ''cold'' pipes ect. once in a while with the Marvel / WD on the rag,, will help ''a lot'' in keeping rust down.
You want to try & wipe most of it off though.
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