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People obsess over methods of thermal compound application but real word differences seem minimal to non-existent.
I change the CPU/GPU paste on several computers every few years, either because of an upgrade or just regular preventative maintenance.
I use Arctic Silver, and the 2-part Arctic Clean. My steps are, using gloves throughout:
* clean the surfaces gently but thoroughly with cotton buds, and then lint-free laboratory wipes (Kimwipes or similar;
* let dry for at least 30 minutes;
* apply the paste to the CPU with a glossy business card (new in box, untouched); spread in X, Y, and X-Y directions so it's a thin even coat;
I don't use the edge, I bow the card in half and use the soft bend as the spreading surface;
* install the heatsink; this step usually squishes the paste a little but not much;
* run a thermal benchmark, to test the installation.
What I find, each maintentance cycle, is that the previous coating was quite even with no obvious voids, and the benchhmark gives reasonable temperatures
on the fully loaded system.
So yes, do it with care - don't scratch the surfaces, and do a proper clean - but don't obsess either.