Rod,

I would very cautious about using any penetrating oils such as WD 40 or Breakfree. Once the oil gets between the paint and the base metal of the core you may find that the paint comes off as the bond is irretrievably broken.

In the gunsmithing trade WD40 has been known to get under nickle plating and cause it to flake off. Paint has even less adhesion than plating.

If you do go the oil route then the oil will ahve to be removed again to do any touch up. Paint nor bluing solutions don't adhere worth beans to an oily surface.

Sometimes leaving well enough alone is the best course.

Good luck.

Tony