I teach airbrush lessons, and always point out good reference material to my
students.  In this part of the country, there is very little opportunity for
hands-on instruction in using the airbrush, and most of the people who come
to me say it is very difficult to find someone who uses an airbrush well and
is willing to teach the techniques.
        Aside from watching someone at the local mall do T-shirts, many of the
artists, art students, and hobbyists I meet have never seen an airbrush being
used.  Often a workshop or a "how-to" book is the only place these people get
to learn about an airbrush.
        I vote to keep the airbrush chapter. The airbrush "look" may not always be
appropriate for an entire finished piece, but in a mixed media painting, I
find there are some parts an airbrush is THE tool of choice for using.
        Also, there seems to be a recent re-engineering of the airbrush, bringing
several new models on the market, which have made a sometimes finnicky tool
easier to use and unclog.  Many of my students bring a box of airbrushes and
parts with them when they come for lessons, and say that they have either had
the airbrush for a long time and never used it, or used it once and it never
worked right again.  It seems to me that  the airbrush  requires more
instruction (at least initially) than any other traditional paint applicator.
        Yes, please keep the airbrush chapter!

Thanks,
Darcy