Once the first coat of plaster is leathery (has dried enough to be pliable, but won't stick to our fingers when we poke it), it's time to "press back." This is where we go over the wall with our trowels, pushing with all of our might to compact the plaster into itself. We're told this breaks the crystalline structures that have formed in the curing plaster, orienting them so they grow together in a stronger fashion.
Finally, we scarify the wall, creating ridges for the second (brown) coat to key into.
Two exterior walls down, two to go!