Just adding in - best char to do this is a lightning javazon. She can kill huge groups at a time, and the king is immune to lightning, always.Both NM and Hell cows drop flawless gems regularly. If you're up to it, I'd do Hell cows, since they can drop pretty nice socketable items as well.
Yeah, very quick way to obtain 4-5 flawless gems per game (Baal games). YOu can also pop a variety of runes, some neat rares, and lots of misc. stuff.Lower Kurast Hell in full games is the best place for this. You dont need any special skills/chars, just pop all clickable objects fast.