wrote:

I have some horizontal flourescent light fixtures that have sockets to
accept horizontal bulbs with 2 pins at each end. in trying to
replace the bulbs, the bulb pins are stuck in the sockets.

would it be useful, and also safe, to spray wd-40 into the sockets
before inserting the bulbs?

It's OK, but generally it's safer to use silicone-based lubes around
plastics since mineral oils will damage some types, such as vinyl
(PVC). Here's a web site that can tell you which chemicals are
compatible with various materials:

www.coleparmer.com/techinfo/ChemComp.asp

Any dielectric (electrically insulating) characteristic of the oil or
grease doesn't hurt electrical conduction in this application since the
metal pierces through the film. This is why it's perfectly acceptable
to apply grease to car battery terminals before installing the clamps
to them.