Thanks, I will do so.

As long as you know what you are doing, a metal tool is OK.  The typewriter trade use(d) a tool called a segment pick which you used to be able to buy.  Many typewriter men made their own by grinding down an old typebar and fitting a wooden handle.  I still use the one I made when I was an apprentice - a secondhand Imperial typebar ground down and stuck into a section of wooden cleaning brush handle with epoxy resin.  It is used to carefully scrape the sides of the typebar slot from bottom to top, hooking out the accumulated dirt.

Have applied more naphtha to the segment, and things are coming around -- maybe another application and all will be good.  I started to feel some of the "bounce" that a reviewer on the typosphere (I forget who) had mentioned -- the typebars would need to be totally fluid in order to get that feeling, so it's coming along.

Whether the typing feel is ultimately something I'd prefer to other machines is as yet to be determined, but for sure this is a very well made machine.  (Mine's a Barcelona model, 374xxx -- not sure what year that would be, since I know the serial numbering on these is confusing, but early 60s, I guess.)

I had the same issue with a machine I acquired recently... Type bars were working, but sluggish, so I applied generous amounts of solvent with a fat artist's brush. Seemed to fix things but the next day many of the type bars were seized up. After several tries at this -- with the same result -- I used a medical syringe to force solvent into the segment -- success at last! I think the solvent initially acts as a lubricant but if the segment isn't thoroughly cleaned the problem returns once the solvent evaporates. I have used super fine grit paper in the segment on one or two machines to get type bars moving when it looked like the issue might have been complicated with rust... And then made sure the segment was thoroughly flushed out with solvent.