How to pour a Black & Tan

Have read about the pouring devices for pouring a Black & Tan. Apparently some device is needed. Just tried pouring a Black & Tan without a device and it didn't work, the Imperial Stout and the Imperial IPA mixing right away. What device do you use?

My Mom actually taught me how to do this. I use a serving spoon (a whole spoon, not slotted) and pour over the covex side of the spoon. Slowly and patiently, of course.

To get on top of the first beer half way down the glass, bend the spoon backwards to make a handle with a horizonta; back of the spoon.  Use a garbage spoon.  (I've actually heated a plastic spoon to make one once)