Well, you can hit first with a right-left swing in the situation I described, but that will just glance (even with a steel pick or warhammer). If you keep him in the centre of your screen, he's running away from your left-right hit, so you have a negative speedbonus, which will make it glance. Overhead is too slow, stab is too slow.
You can turn into your swings, but I consider that a bit more of an advanced dueling technique and not something you should start with as a shielder.
On that note, maybe you can give me some advice on that part. I've been practising that on the duel server yesterday and I find it very hard to turn into my swings as deep as others do without losing track of the duel.
Try strafing in the same direction as he is, looking slightly to his right, and left swinging. If at any point you think you might have messed up the timing, then play it safe and block.
Eventually you will be able to tell when somebody is going for a castor based on their footwork, and the counter will become second nature.
What vodner said. And you can actually overhead or stab them too once you get the hang of it.
Don't do a right swing. Try not to do them unless they are far away from you and it will be a perfect sweetspot hit.
ghostie, if you want a courser you can do this too.
Level 30 (4 420 577 xp)
Strength: 18
Agility: 18
Hit points: 57
Skills to attributes: 2
Ironflesh: 2
Power Strike: 6
Shield: 3
Athletics: 6
Riding: 6
Horse Archery: 0
Power Draw: 0
Power Throw: 0
Weapon Master: 6
One Handed: 1
Two Handed: 1
Polearm: 154
Archery: 1
Crossbow: 1
Throwing: 1
Note: The balanced cav build. shield and IF distribution is up to you.
And about turning into your attacks, don't go wild like that. Your character can only turn at a certain rate. If you're wildly swinging it around faster than it can turn, you'll just lose track of everything. What vodner said is the easiest thing to try to do.
Another trick is to simply kick them when they sidestep & double swing you. That takes some practice in the duel server to get down, but what you have to understand is this: When they go for a double swing, their second swing on your right side they have to be touching you. they HAVE to be in kick range for it to be fast enough to hit the untrained player. Any player that gets that close automatically opens them up for a very easy to do kick. As soon as kicked, you get a free swing on them.
I don't necessarily recommend you doing this yet, but keep it in mind to learn later In a duel server.