ProcessDocumentAction (with the right post data) did the trick? That is great info -- I am going to go look at the documentation on that resource right now...
You mentioned new posts not showing up -- is it possible your account was a trial run (like a cloud demo) and has since expired? If so, you will need to use a different login to be able to post again. The same thing happened to me, and I was told I needed to register with a new email address, and my previous posts could not be linked to the new credentials. You will have to contact DocuWare support for that.