[lathspell]

If I understand correctly, Rune Son of Bjarne, you wonder about to things and those are mixed up a bit:
1. How come the Elves never found a way to kill Glaurung?
2. Why did the Dwarves manage to drive Glaurung of the battlefield where the Elves could not?

I think that the answer to your first question is, I believe, fairly simple. Glaurung, as father of dragons, had the same protection as others. That means he had the same hard scales as, for example, Smaug. The only problem that those dragons had was their soft belly. Glaurung probably had the same soft spot, as we see when Turin finally slays him. Glaurung however couldn't fly, so his 'soft spot' was never revealed. His armour kept him alive. The only time that someone managed to see his belly, it was fatal for Glaurung.

The answer to your second question is, as is already said, that Aulë maid the Dwarves in the dark times of the world. Therefore he maid them strong, stout en far more resistant to fire, corruption and I believe even magic (the seven Rings of Power, for example) than any other race. With this natural advantage comes the fact that the Dwarves made armour that Elves could not rival.
With these two added the Dwarves were far more resistant to Glaurung than any other, save perhaps the most powerful Elves and Men. I think that this is the reason that the Dwarves managed to drive him off, being harder to destroy than the others, but the Dwarves couldn't kill him. They didn't manage to get through his armour, just as the Dwarves of Erebor could'n't pierce the armour of Smaug.

Greetings,
lathspell