I am sure that no matter what the thermal paste you use, the thinnest coat that fills all the air spaces. Ideal would be perfectly flat die and heatsink and then you would need no thermal compound to achieve optimal heat conduction. Matching two lapped surfaces is ideal, with the absolute thinnest coat of thermal paste (used simply to fill the microscopic valleys that are in the two surfaces ) as possible so more of the two surfaces touch each other instead of the extra interface material (thermal compound) If the one or two of those surfaces are not flat then more is needed to fill the air gaps left by the bowls and hills of the not flat surface, thats why more may work better is some cases.
But ideally, if you are sure of your mating surfaces, then a transparent coat is optimal, the air bubbles in the compound will be smaller.