I suggest that if you like this scope be very thoughtful about heat and exactly where your penetrating oil might creep.If it finds its way to any mechanical joint ,threads,or screws on the scope you may contaminate the inside.
I would lose the heat idea.Old lenses were laminated with balsam.You never know where newer scope may use superglue or equivalent.
How are you applying the oil?If on the heads,it may not have a path to the threads.Are the threads blind holes,so you do not have access from the bottom end?You might try the ring gap,where it is split.Maybe a thin hypodermic needle,or use an oil wet thread like dental floss,or? just figure a means to make a controlled application that makes it to the screw threads,but does not run down the tube.
Kroil is pretty good stuff.KW Knock-R-Loose is pretty good.I have not used it,but some say wintergreen oil.
Some O-rings and seals dissolve in acetone.
On the "Now I have to find a Gunsmith"....
I'm smiling as I say this,and hindsight is 20-20.Have you ever wondered why Gunsmiths can seem crotchety?Look at you over the top of their glasses,or even squinty eyed?I know one named Carl would probably ask you why you didn't bring it in before you lost the screw head?
I'm not trying to be a jerk,just an observation on Gunsmiths.
