I could maybe add something like this, but I could be off the mark here..
Working with patches
Sometimes a Debian maintainer will use patches to enable systemd support or systemd related feautres in packages.
Check the series file for patches.
$ cat debian/patches/series
In the best case scenario you can remove patches that are applied at build time using quilt.
$ quilt delete systemd-patch.diff
Other cases are more difficult.
[explanation about removing patches already applied to sources, no idea about this]
You can now remove the patch from the
$ rm debian/patches/systemd-patch.diff
[more specifics needed]
[something about applying patches..]
The quilt format
working with the native quilt format
[mention how native packages can use the git format]
[incorporate quilt format packaging]
[no clue about the steps yet]
creating a pristine tar
creating an original tar
I will add to this as I work these parts out.