Thanks for reaching out to us! Not all tools and effects have “Effect Painting”, however in order to just lighten a face you can use the Pro tab > Pro Adjust tool. Increase the exposure and then tick “Reverse Effect” on the Effect Painting dialog that shows. You can then paint over the face (by dragging with your mouse while holding the mouse button down).
If you can’t see the Effect Painting dialog make sure that the “Effect Painting” button within the tool’s options is on.
Regards – The Ribbet Team