debianinzing some source packages from a local mirror

[Albretch Mueller <lbrtchx@gmail.com>]

 Often I need to make changes to Debian source files, so I was
thinking of having my own partial source mirror

 I have been reading on how to do that and I have found some
inconsistencies between the German version of Debian docs (6.11.2
"Partieller Spiegel", which I read and annotated some time ago), the
English docs and other sources on the Net, which makes me wonder about
what may be out there that I don't know (I have search too, but still
can't find good information on how to do this)

 I think basically all you need is:

 1) find out which packages' sources do I need. (I think I read
somewhere about making apt-get do a dry run to find out)

 2) get the sources and stash them locally along with their official
consistency data (md5sums, signing keys, ...)

 3) get the build dependencies among the source packages (from where
do you get that graph?)

 4) somehow use 3) to sequentially build, make and install packages

 5) keep track of the cruft that may be created to then remove it

 6) periodically "go to the source" and/or register some deb-src
mailing list in order to update your own mirror if necessary

 How do you achieve this?

 Thanks
 lbrtchx