Apt-move and pgp signing

[James Vahn <jvahn@short.circuit.com>]

I read with interest about dfsbuild and would like to try it, but it
wants a Packages.pgp file from my local mirror. Setting apt-move and
gpg up for this is proving to be difficult.

        short:~# gpg -K
        /root/.gnupg/secring.gpg
        ------------------------
        sec   1024D/C633A12A 2005-09-24
        uid                  James Vahn <root@short.circuit.com>
        ssb   1024g/14633FD3 2005-09-24

In /etc/apt-move.conf is this line:

        # Set this to key name to be used for signing Release files.
        SIGNINGKEY=
                   ^^^^^^^^
What is it wanting me to put there? What does "key name" refer to?
This is the command that apt-move uses:

        [ -z "$SIGNINGKEY" ] || gpg --detach-sign -ao Release.gpg
        --default-key "$SIGNINGKEY" --batch --yes --sign Release

This is from the apt-move manpage:

    SIGNINGKEY=
           If this is set to non-empty string, then packages will sign gen-
           erated Release files  with  specified  signing  key.   You  must
           install gnupg before enabling this option.  With current apt you
           should list compression none in PKGCOMP directive, otherwise apt
           will complain about missing files.

And this from the gpg manpage:

    --default-key name
             Use  name as the default key to sign with.  If this option is
             not used, the default key is  the  first  key  found  in  the
             secret  keyring.  Note that -u or --local-user overrides this
             option.

I can't make sense of it, all clues appreciated.  thanks!