Bill Tindall, E.Tn.
Lube not only has to have low friction, it has to stick to the screw. In this regard soap is seemingly ideal, but not. While it is not hygroscopic, it does retain water, and it is a good conductor of electricity, which leads to it being the equivalent of storing the screw in dilute salt water.

Paraffin is a good lube but it doesn't stick well. Bee wax is good at lube and sticking. But best of all by a wide margine is the tube of wax used to lube the blade of a metal cutting band saw. These tubes, about 1 1/2" x 12", are available from any machine shop supply, MSC for example. This sticky wax adheres to screws and the difference in driving torque is remarkable. You might be able to beg an inch or two of the remains of a tube from your local machine shop. That's where I got mine.