Mention of Sozzle brings back memories from long ago.
Very effective.
Probably what is used by the military when putting items into store, and not easy to remove.
(We used to use a steam cleaner when stripping engines for the routine check after about five years in store before reassembly and reprotection ).
WD40 and its look alikes tend to contain a high prportion of solvent, and little oil, but will penetrate into less accessible areas.
VPI is effective, but being a vapour can dissipate over time.
For measuring instruments I have used a lanolin based product, (Bought from Chronos; a long time ago)
It is VERY sticky, and is best squeezed from the tube after it has been warmed and thinned in HOT water.
For other applications, such as machines, the objective is to seal out moisture and oxygen, to prevent corrosion.
WAXOYL, possibly heavily diluted with white spirit, will be very effective. After, it can be removed by further application of white spirit.
Spraying my ML7 with ordinary lubricationg oil produced a grey emulsion of oil and moisture after a short time, so would be wary of just using oil as the protection, since it seems to be a risk after not too long.
Spreading grease over surfaces is labour intensive, (and you have to be careful to cover every exposed area ), but is effective.
Howard