if the bronzer is at least 2 shades darker than your skin tone and not too sheer, it should work as contour. And the lighter color could work as a highlighter if it is 1-2 shades lighter than your skin.
Here's what I'd do:
*Use your index finger to find the bottom edge of your upper jaw (some people prefer to suck in their the cheeks and make a "fish face" then they apply contour color to the hollows of their cheeks. But that puts the color too low on the face for me). Just sweep the stick on the bottom edge of your jaw, starting from your ear and stopping no closer than 2 fingers' width from your mouth. Blend out the edges of the color to get rid of any harsh lines. Sweep some color on your temple, near your hairline and along your bottom jaw, and blend.
*Sweep the highlighter on your cheekbones at the highest point (where they jut out most from your face) and blend to soften. You can then apply your blush between the highlighter and contour to tie it all together.