Use naptha - AKA lighter fluid or Ronsinol. 'White gasoline' also works - but work outside with a fire extinguisher handy. Shutters will work fine dry. Sometimes a minuscule drop of mineral oil applied with an oil-dampened toothpick is needed on the escapement of the slow-speed and self-timer mechanisms.

Do NOT use WD-40: it will dry out and leave a sticky gum. WD-40 was designed for rustproofing newly machined metal - it penetrates, displaces water and then evaporates, leaving behind a gummy coating that keeps the metal from rusting. It happens that WD-40 is great stuff for freeing up gummed up mechanisms - it is after all a gum solvent. To keep a mechanism ungummed you need to follow the WD-40 with an application of real oil like SAE-30.