If you want my suggestion?
Take you a well-laminated card from a deck of poker cards. One that is flexible, thin, and well coated with plastic as not to stain it.
Put a drop of Arctic Silver 5 thermal compound about the size of a grain of rice on the center of the top of your CPU. Then, take the playing card and spread the grease one direction (meaning, left-to-right, or top to bottom) as to make sort of a band of compound across the top of your CPU.
Then, spread the perpendicular directions to that band of compound to spread it across the top of the whole CPU.
Note: The reason I say to use a plastic-coated playing card is that it is VERY flexible and will bend to somewhat of a flat surface and distribute the dragged thermal compound more evenly. It is also easier to get the compound thinner with a flat surface than a hard edge, as is found with using a credit card.
Good luck with this. If you do it right, it really makes a difference.