Having to fit all liquids in a quart size bag can be a challenge. Consider buying Nalgene brand bottles as they are truly leakproof. You can also buy .5 ounce bottles, which will hold plenty of shampoo, conditioner, etc. for even week-long trips. They take up much less room than the standard 1- 3 ounce bottles that usually remain halfway empty. You can buy them at the Container Store or online.