Best Practices for popup windows

Hi,

I'm trying to create a menu system where the entire screen is temporarily taken over, while the player remains 'in' the world.

For example, you walk up to a barkeep, and the 3D game cuts to a 2D picture of the barkeep with some words on the screen, and a button to accept and one to cancel. When the screen goes away, you resume playing.

What I have been doing for the last umpteen years is creating a prefab of the UI elements, and turning them on and off. I did that with nGUI and now uGUI, and I assume that's just how it's done.

But I'm curious if anyone does something like this, with the addScene additively. Is that a better way to do it?

Thanks!
-Chilton