1. Hair that has not been freshly washed seems to work best
2. If you have short hair and pieces start to stick out a simple bobby pin that matches the color of your hair will do the trick, also try using a smaller sock.
3. Use a sock that is similar in color to your hair (just in case a little peeks through) this is especially helpful if you have fine/thin hair
4. If some of the sock does happen to peek through before you take the whole bun out and start over try moving pieces around spreading your hair out nearby and bobby pinning/hair spraying to cover the exposed area, its much quicker!