1. Open your image (CTRL + O)
2. Double click on the lock, to unlock the layer
3. Rename it to “Original”. Click OK
4. Duplicate original layer (right click)
5. Double click on the text “Original copy” then rename it to “sketch”
6. Click the eye icon next to “Original” layer to make it invisible
7. Click on paint palette, change foreground to black. Click OK
8. FILTER > SKETCH > STAMP
9. Zoom out to get a better view using (+) (-) icons on bottom left
10. Adjust light/dark balance and smoothness until you are satisfied with the amount of detail and sharpness in your image. Click OK
*NOW YOU HAVE A SKETCHED BLACK & WHITE VERSION OF YOUR PHOTO*
NEXT STEP IS TO COLOUR YOUR IMAGE
11. Highlight “Original” layer, click eye icon to make visible
12. Make “Sketch” layer invisible by clicking eye icon next to it
13. Select eye dropper tool CTRL + I
14. Click on skin to sample colour
15. Reverse visible layers by clicking the eye icons so that the original is invisible and the sketch layer is visible
16. Select brush tool CTRL + B
17. Create new layer, should be above “sketch” layer.
*SHOULD BE PAINTING ON THE NEW LAYER*
18. Click and hold to brush, all over face, ears, neck. Avoid lips Eyes. Don’t worry about mistakes, excess can be easily erased later
19. Change blending mode to MULTIPLY under layers tab
20. Select eraser tool, select hard brush, erase excess parts of airbrush
21. When finished, right click on layer we just airbrushed and click “Merge Down” (this will merge it into sketch layer below it)
NOW YOU HAVE A SKIN COLOURED VERSION OF YOUR CARTOON
NEXT STEPS ARE TO COLOUR IN LIPS AND EYES
22. Reverse visible layers again using eye icon to make original photo visible and everything else invisible
23. Select eyedropper tool and select colour from lips.
24. Select brush tool: CTRL +B
25. Reverse visible layers using eye icons
26. Create new layer, should be above “sketch” layer.
YOU SHOULD BE PAINTING ON THE NEW LAYER
27. Paint over lips
28. Change blend mode to MULTIPLY in layers palette
29. Right click on layer 1 and merge down
REPEAT ABOVE STEPS FOR EYE COLOUR
Source: Tutorial