VALOO aperture ring hard to turn

[summar]

I've used a VALOO enlarger accessory as a hood on an Elmar 50/3.5 for a long time. Over the decades the aperture adjustment ring has become more and more difficult to turn (no surprise). Is there is a way to free up the ring just a wee bit or should I leave well alone?
Any suggestions much appreciated.

 

[Ronald M]

DAG or Sherry

 

[Mr_Flibble]

Small drop of zippo fuel

 

[greyelm]

This may sound like heresy but I think a small squirt with WD40 may help. Despite arguments to the contrary it often works.

 

[Luddite Frank]

A second vote for lighter fluid. WD-40 would probably be okay too, although I wouldn't use it on a focusing mount or inside a shutter assembly.

 

[summar]

I used lighter fuel in a hypodermic syringe -- worked well. Thank you everyone.