Thanks. I'm sorry, but I'm still a bit confused about the procedure.
I've downloaded the sha256sum file as you've instructed, but can't find your public key. Would that be something equivalent to Alan's key ID '98832223'? i.e. would I enter the following?
$ gpg --recv-keys --keyserver keyserver.ubuntu.com **your key ID**
$ dpkg-sig --verify armory_0.94.1_amd64.deb