1. Start by opening your existing car image you want to edit.
2. My original image already had a small existing vent, so zoomed right in and using the Lasso Tool I made a selection around this and filled with black.
3. Create a new layer.
4. Now using different selection tools mark out a shape similar to my example. You can also use the Lasso tool if you find this easier.
5. Grab your Air Brush tool and set it to around half the size of your selection (mine was about 45px) with Black as your colour and at around 16% Pressure/Flow. (If you have a new version of Adobe Photoshop, you may be required to select the normal Paint Brush then there is another button on the toolbar to Enable Airbrush Capabilities).
Now taking your time, start from the black hole and work your way outwards. Apply more strokes closer in towards the hole to give it a deeper look. Here is my final close up, and final image.
More Tutorials: 
