I have spoken at some length with Tony Leach about the best lubricants and he recommends a tiny amount of silicon oil+STP blue+WS2 for the inside of the compression tube of HW77s/TX200's and other sliding compression tube airguns.
For standard spring guns a smidge of STP blue+WS2 is good for lubricating the piston seal in the compression chamber.
For metal to metal a light coat of high moly paste(50% plus)/light grease is a highly recommended option.
Tony Leach makes a very good point of advising against super thick greases where tolerances are close(such as the inside of the spring guide) as the grease may grab and cause inconsistent/low velocities.
Well supported springs do not need masses of heavy grease.