I salvaged some frozen barrel adjusters (they were in Excellent condition and shiny, but frozen) as follows :
(1) I removed the O-rings and clamped the round nuts in my panavise which has plastic jaws.
(2) I used a safety pin to dig out the rust from the barrel adjusters.
(3) I gently rocked them back and forth and sprayed them with WD-40 and/or soaked them in evapo-rust. I was able to free the adjusters, with great patience (maybe 15 mins total over a period of days.) Don't underestimate the benfit of digging out the rust with a safety pin, that really helped the most !!
- Don Gillies
San Diego, CA, USA