Ancient Rhetoric and NT Documents

Ben Witherington on his blog lately has been emphasizing the worthwhileness of understanding ancient rhetorical techniques to aid in our understanding of the New Testament documents. He posts an interesting lecture he gave on the subject.

I have myself found that, in general, understanding better the social and cultural background of the New Testament has helped immeasurably in my understanding of it. That said, I recently read Witherington's allegedly "Social-Rhetorical Commentary on Romans" which failed almost completely to make any worthwhile use of insights about rhetorical techniques and structure (he talked plenty about rhetoric, but it was of no actual assistance in understanding the text), so that tempers my enthusiasm for understanding rhetoric somewhat. I confess, however, to being almost totally ignorant of the structures and forms of ancient rhetoric. So I intend to attempt to remedy this by studying the subject.

I am a bit unsure where to begin my study of ancient rhetoric. I would have thought they'd be a book designed for Classics students titled "An introduction to the standard forms of ancient rhetoric" or "Types of Greek rhetoric and their structures" or something similar. But searching of Google and Amazon has yet to reveal such a book to me. So if anyone knows of one, please sing out. Lacking helpful secondary sources I'm thinking I might start by reading Aristotle and Quintilian on rhetoric.