Well, you've gone beyond my direct experience. However, generally, if there's a way to do it on the command line, there's a way to do it in webmin. In this case I could be wrong, however: DNS is not my forte.
It's pretty trivial to install webmin and uninstall if it doesn't suit your needs. It has a pretty robust Bind DNS module, which is the most relevant information I can provide (I've always done TXT records through my registrar). Perhaps someone else can recommend a better product or confirm my recommendation.