Quoting Sean Whitton <spwhitton@spwhitton.name>:
Just `git clean -xdff && dpkg-buildpackage -S` and dput the result, or (easier) `dgit push-source`.
I prefer to build only once, if possible, generating both binary and source .changes. Both in a clean chroot. Then I can try out my .debs and on success just sign and dput. Works fine for me with pbuilder.