[AUCTeX] Tex-Master (faq ?)

[Mister Woody]

Hi!
I apologize if this is a faq, but I couldn't find the answer anywhere...

At the moment I have:
(setq TeX-master "main.tex") ; Query for master file.

and from the doc, I know this:
----------------------------------------
If AUC TeX finds the line indicating the end of the header in a master file
(TeX-header-end), it can figure out for itself that this is a master file.
Otherwise, it will ask for the name of the master file associated with the
buffer. To avoid asking you again, AUC TeX will automatically insert the name of
the master file as a file variable (see section `File Variables' in The Emacs
Editor). You can also insert the file variable yourself, by putting the
following text at the end of your files.
---------------------------------------

Now I don't want to use any "File variable", since I share the .tex files with
other people. At the same time, I would like to use the name "main.tex" only for
papers that I have \input inside.
Otherwise I would like to use Tex-Mister just as the current buffer. 
Is there any way to do that, automatically? 

Thanks, 
Mr. Woody