The secret to a perfectly smooth hummus is peeling the skins of the chickpeas off. It is definitely time-consuming but makes a HUGE difference. If you hold each chickpea between two fingers and pinch it a little, the skins will sort of just pop off. It adds about an extra 8-10 minutes to the prep time, but I think it's worth it.  You can make the hummus with the skins on, but it will not have the same smooth texture. Besides, my kids think it's fun when they pop out of the skins and they like to do it.