Grain of sand puts too thick of a layer to completely cover the cpu.
Also, correctly applied, I've never seen it 'completely' cover a 'modern' cpu...in my experience.
Factory applied it usually misses ALL 4 corners. If you use enough to 'squish' it out over the 4 corners...you've used too much.
I usually use ~2 grains of sand sized drops, but when they are spread with a STRAIGHT edge, MOST of it ends up on the straight edge. Its an even, see-through light grey layer of AS5...too much and you loose anywhere around ~3C