Re: backstay adjuster maintnence.
I'm assuming it's a hydraulic adjuster? Who makes it?
In anycase, taking it apart and having it powder coated is the best bet.
You can clean it up and use a two-part paint like Perfection
Or you can clean it up and use a cheaper one part like Brightside. It probably doesn't get banged up back there too much so brightside might work out fine.
Make sure you use the correct primer for the material it's made out of.
Merit 25 # 764 "Audrey"