I seem to be cursed at the moment with watches that dont want to disassemble. last time it was a Citizen diver case back, now its my recently acquired Golden Tuna ssbs018 which came with some chips on the crystal. I located a NOS replacement and today tried to remove the Phillips headed shroud screws. After a few seconds I realized that it wasn't as easy as just unscrewing them as they clearly have some form of locking compound applied to the screws. I decided to apply some local heat to soften the gunk, using a screwdriver that I heated over a flame and this did the trick with three of the screws. As always however its always the last screw or bolt on a watch or car that seems to be the awkward bastard and this is no different. Using the heated screwdriver repeatedly had no effect, tried using boiling water applied locally with the same outcome, gentle tapped with a hammer and also nothing, the screw is started to get a bit gnarled by all this attention so now Im having to rethink and also give it a rest until tomorrow.

Has anybody tried applying freezer spray in these situations to shrink the screw enough to break its seal with the thread on the shroud? The alternative its to get more aggressive with the local heat using a fine tip on my soldering iron but I wanted to keep this nuclear option as the last resort.
Thanks
Keith