Still Air is a pretty good insulator. Air bubbles in thermal paste are bad. So how to minimize air bubbles in the CPU/ heatsink interface ? A Vaccume chamber. Put the paste CPU and heatsink into a chamber. Draw as hard a vacuum as possible. As the pressure drops any bubbles in the paste will increase in size as the air inside them expands to fill the abhorrent vacuum. Making the bubbles want to float up through the paste (whose density does not change) more energetically. Hit the paste with a bit of ultrasonic to help the now big bubbles burst. = reduced air content paste. (there will still be air pockets but there WILL be less insulation.) Then apply the paste as normal (in the chamber) & mount the HS to the CPU, as normal. All of the air bubbles trapped in the space between the contact surfaces will be low pressure bubbles that contain fewer air molecules than bubbles of the same size in ambient pressure. Vent air into the chamber to bring the air pressure up to ambient and all of the remaining bubbles will shrink in size, drawing the paste in to fill the volume of the dwindling bubbles.