Producing interactive PDF forms from DocBook content with XEP

We have a large amount of PDFs generated from modular and singlesourced DocBook XML, and need to expand that portfolio with ineractive PDF forms.

All trails lead back to http://www.renderx.com/reference.html#PDF%20Forms, but they do not say what we need to do in our DocBook XML and XSL files to achieve this.

Do I need to become an XSL-FO expert and write the .fo file by hand?

Do I need to rewrite the XSL to pull something out of the existing XML files? And do I need to add special markup in the XML for this?