For glass bedding a barreled action to a stock or a scope mount to an action, many things will work as a release agent.
Asking what is the best release agent for gunsmthing is like asking what home found object makes the best door stop.
But for industrial purposes, there may be additional constraints.
I have designed a lot of aerospace magnetics [like transformers] that were potted in many sequential stages with many epoxy like products to get matching thermal expansion, good thermal conductivity, and resist shock and vibration.
These processes are often proprietary, but usually include a vacuum chamber. They cover objects in epoxy. They pull a vacuum. The trapped air forms huge bubbles that rise to the surface. They break the vacuum. The epoxy rushes in and fills the voids. The epoxy is allowed to cure in an oven. Then on to the next type of epoxy product used in layers.
Maybe that is why Boeing so often uses high vacuum grease release agent for factory tooling epoxy, when, like with gunsmthing, anything will do.
They already have the stuff lying around.
I have used it on guns, and it is no better than whatever is within reach, like reloading case lube.
http://www.mrsilicone.com/HighVacuumGrease10.html High Vacuum Grease - 10 (H.V.G. 10)
..Applications:
...
7. As a release agent for eposy, polystylene, polyvinyl chloride, polyester resins and other plastics. Normally it is used only when common release agents including other silicone release agent fail
