If you want to learn blocking properly and quickly I recommend starting up Native and clicking the tutorial. There are bots in there of various ranks. Start with the novice one I believe, and put combat speed to slowest in the options. Focus on blocking him only until you can block atleast 9 out of 10. Then go to the next bot who is called veteran I think, do the same again. Work your way through the bots from low to high and if you are confident on blocking them all, you turn the game speed up. Start while standing still, then start moving around while you block him.
If you can block the highest rank bot confidently on normal game speed, then youre ready to go to the duel server and fight real players. Although you also might want to practice blocking and then attacking back. You can also try blocking them on the faster settings, but in the end practising against the AI is only for the basics and blocking real players is a different ball game.
Try to block with as small mouse movements as possible and hold down your blocks, not just click em.
