Thermal paste. How much?

I have looked at videos on the 'net and they seem to use small pea sized
amounts of thermal paste spread out. Yet when I tried this the tutor
(although it is an open learning course we do have a few workshop
sessions)told me to "stop messing around " then he basically covered the
entire surface with stuff from the syringe ie he didn't seem to spread
it out at all. Does anyone know the correct amount of paste to use.
First principals tell me the tutor is wrong, and that only a small
amount is needed, and as it is conductive it shouldn't squeeze out from
under the heatsink.

 

Your instincts are right; the correct answer is to use very little
thermal paste.

If you do it right, the paste spreads out to a layer no thicker than a
sheet or two of paper, and at that thickness, it takes very little to
completely cover the top surface of the CPU.

Too much past can cause multiple problems: First, it may not spread
thin, and a thick layer of paste is NOT a good thermal conductor and may
impede the cooling system from properly transferring heat from the CPU
to the heatsink. Second, the past may ooze out from the CPU completely
and get all over the motherboard, where it may both make a mess and
cause many kinds of problems (many of these are conductive, but even the
ones that are not high conductive will cause problems if they get on the
motherboard components right around the CPU).

The correct amount is about the size of 1 to 2 grains of rice.