twins and stairs

How do you twin moms carry your babies up and down the stairs of your home? I'm going to be a FTM and don't know what I should plan on doing. I have a long flight of wood stairs. Definitely planning on getting socks that grip, but what else should I do? Do you carry one at a time, two at a time or wear one with some type of wrap/sling (while holding the other) or wear both?