Depending on where you are contouring on your face decides what brush you use. 

For cheeks, jawline and hairline: Apply with the Colour Basis "Shade It" angled contour brush on a freshly powdered face, making sure to tap brush to remove excess colour before application. 

For nose: Apply with Contour It brush. Contour must be added sparingly and carefully blended. Practice at home in daylight to test progress. Subtlety is key in contouring, you never want to "see" it.  Always contour your face immediately after foundation/powder application.