Draw new or extend existing Face Sets with each stroke.
Holding Ctrl will continue drawing the same face set as the one under the cursor. Holding Shift will relax or smooth the edges of the face sets by modifying the underlying topology so edges flow along the perimeter of the face sets. This will remove the jagged lines visible after drawing or creating a face set.
While a lot of the general brush settings are supported, it's not needed to change them from the default, as the brush purpose is very simple.