I found this link.

Step 1: Get a foto of your car,something medium resolution is good, if the foto is two low then the cars parts will look odd, if its a crazy detailed , the final product will look più fake. The foto im using is at the bottom of the screen.




Step 2: Go to the cars wallpaper site-- link and find a car mouth and eyes that suit your picture. It dosent mater if the car is facing left o right, o the perspective angle, we can change all that later. for this one i'm using Flo. Open this wallpaper at the highest resolution.



Step 3: with your CARS wallpaper and using the freehand...