I highly recommend Dr. Tung's dental floss.

I think once you start flossing, you just can't go back to it. I originally started with a different brand, but it didn't seem to remove debris very effectively. So I tried the Dr. Tung's floss that was recommended to me, and honestly, there is no floss quite like this one. It costs about 6,000 won and you can buy it at Olive Young. I highly recommend giving it a try. I think I've used about 20 packs so far. Brushing is important, but you absolutely must floss as well.