1. Deadangling; We did this with unupgraded weapons. I hold down block and he starts his attack and turns away before the attack hit me making it hit through my block. We did this with a lot of different weapons and angles. Then some duels with upgraded weapons focusing on achieving this.
2. Combos; Essentially the same as deadangling, I hold down block for the first hit, and then try to roll, block or parry the consecutive hits. The point was to keep me in a lock for as long as possible we used weapons like Murakumo, claymore, zweihander, trying to alternate between straight hits, deadangles, and 2handing. This was a lot of fun and made for some epic combo's (especially with the murakumo). We did some full duels after this as well.
3. Backstabbing; We did sprint locked backstabs and unlocked backstabs on both moving and still targets. It really helped him find the angle and understand when you can punish opponents (parry, running attacks, standing still). Again duels.
4. Parrying; Basically I would have him raise his shield, and do three attacks and tell him to keep his block up and not parry, but say out loud on skype when the parry should hit. This gives him a physical respresentation on his screen (because of the lag I can't say "when my weapon is this far") of when to press the parry. Then he would try to hit those timings after seeing it a few times. At first he failed miserably, but in time he was making 5-6 parries in a row. Again duels.
Basically we went over this in the course of about 90 minutes, and his dueling just improved by an incredible amount. I need to mention that he had no pvp experience whatsoever, so he was going to get better either way just by fighting. Nonetheless, I was impressed with his ability to punish backstab, and deadangle combo me to death on a few occasions. He was too scared of parrying me in the real duels just yet though, so we would need to work on that some more.
I would actually advocate using unupgraded weapons or less upgraded weapons over the calamity ring because it changes your playing style too much. With the ring you will play incredibly careful because you have a chance of getting caught in a backstab, parry, stagger that will end the duel. This eliminates high risk/high reward play, which I believe is a good inidicator of skill. If you can't practice playing agressive, or certain hard to land moves because fear of dying you will get stuck in the turtling, dwgr, backstab style of playing. To practice I would say make fights longer, not shorter.