How hard do you push down exposed aggregate?

If you're pouring concrete, and you don't want the aggregate exposed, you work the top of it with a bull float until the liquid cement rises to the top. You do that by moving the float over the top (floating it), not by pushing down.

If you want an exposed aggregate look, do the above then, when the concrete has set but is still damp, use a hose set to mist and wash the surface until the aggregate is exposed.