Material is screened onto the Intel-provided heatsinks.
Third party kits tend to leave it to your
imagination. They provide a tube of stuff
(so it's not already applied to the heatsink),
and the people who are prone to buying third-party
coolers (me), provide their own tube of favored stuff.
I use the rice grain method, then use an inspection mirror
to check that the paste made it all the way to the
edge of the gap between CPU and heatsink. You want
to "see white" where the gap is, but not "see stuff
oozing all over the place" as that means you applied
too much.
The purpose of paste is to fill any air gaps or blemishes
in the surface, so the two surfaces are in contact with
one another. Building an "Oreo-cookie" defeats the
purpose, by increasing the thermal resistance through
the excess paste.
More info here. While I started by using the credit
card method, I've since switched to the rice grain
(middle dot) method.
http://www.arcticsilver.com/methods.html
Some paste products are thick enough to be like
cookie dough. And are just about impossible to install
properly. They do that, to prevent "pump-out", but
there's a limit to how thick the stuff should be.
Paul