This tool allows you to interactively groom hair along the surface of your geometry. This tool is different from Comb on Screen, as it allows you to groom along the surface of the geometry. The Comb on Screen shelf tool lets you groom the hair freely in the viewport.
This tool is useful for shorter hair that is close to the body of your character, such as grooming fur on the back of an animal.
Using Surface Brush
Click the Surface Brush tool on the Grooming tab.
Select the guides you want to groom, and press Enter to confirm your selection.
Hold and drag along the surface of your geometry to comb and style the hair.
You can change the Strength parameter to give you more control.
Scrolling the mouse wheel or holding ⇧ Shift while dragging will let you resize your brush.
For specific parameter information, see the Guide Groom help.