The best thermal path is metal-to-metal, so you want the paste to be no thicker than the surface roughness of the material itself. This is typically less than a few ten-thousandths of an inch. Fill in those large gaps around the pipes if you like, but wipe the flat surfaces flush. I wrap my finger in some clear plastic food wrap and wipe the surface of the metal with a small bead of thermal paste. Rub the paste "into" both mating surfaces completely, then wipe off the excess.
This problem was caused by Windows, which was created by Microsoft Corporation.