1 Go to layer 2, go around the lines with lasso tool,
then fill with any colour of choice.

2 Once the basic colour has been confirmed, it is then
time to concentrate on building up detail. Examples of detail,
would be the lighter edges on the top halves, shading in the
bottom areas etc etc. I shall show you first how to make the
arches the arches above look as though they come away from the
bodywork, and curve around. This is simply done, using the
following steps:
First lasso around the indicated
areas
Select a slightly lighter colour (for lighter areas)
Select appropriately sized airbrush
(indicated) and brush around the TOP halves of the bumper (in
this case)
Here's
the same picture after I've added lighter and darker areas for
the shading.
It is a good idea to look at the original image to see where
light and darkness falls on the car, so that it can be followed
through onto the cartooned image.
This is all done using the lasso tool (as a mini mask) and the
airbrush tool. Other tools, such as the blur tool etc, can also
be adopted for use when cartooning.