Hello... I always spread the paste flat, So try a "Thin Even Film", spread with your Finger... Air pockets/bubbles will cause problems.
Thermal paste is a " WET " medium to replace the AIR, where metal to metal contact is not possible... AND using too Much paste is not better here.
It can take time ( week ) for the Paste to spead out and allow metal to metal contact agian between the Cooler and CPU.