That's not really what I was asking. In a fight with DGQB, what should I observe from him? What does he do to defeat me?have you read XAJH? In my opinion, it's most likely what is represented by DG9J's formlessness and "overcoming technique with no technique", as explained in length by Feng Qingyang to Linghu Chong around chapter 10. Jin Yong probably hadn't fully fleshed out those ideas yet while writing ROCH and simply used the vague term "overcoming the sword without a sword". I really don't think he meant the phrase literally, as in no-sword, because as the ideas evolved through his discussions with Gu Long, they came to fruition in his later novel XAJH.
Lav and I both postulated before that DG9J was probably the sum of all of DGQB's martial arts philosophies compressed into a set of teachings, because it seems to encompass all the sword stages that Dugu went through. Of course, eventually landing him in the realm of "overcoming the sword without a sword", or formlessness, which seems to be a generally agreed upon consensus of the highest level of martial arts in the later and more mature martial arts writings of Jin Yong and Gu Long.