In Italian, "fa presto" literally means "make quickly." It became a painting term when the father of Luca Giordano (1634-1705) urged his son to speed up his studies.
The term became a nickname for Giordano, and more broadly, a byword among baroque painters like Tintoretto (self portrait, below) who were seeking a more spontaneous handling.
In a fa presto technique, the composition is established quickly over an earth-toned ground with no preliminary drawing. The paint is laid on thinly in the darker areas and broadly and generously in the lights.