New Guy, Question Hiding LED tail lights.

Hi there, Looks like you guys have a great site here, wish I found it earlier.

I am building a car pretty much from the chasis up and I have an idea I have seen and herd about but I am not sure exactly how to do it.
Have you ever seen a car with LED taillights that are hidden behind a layer of piant so when there off you can see them but when you step on the brake pedal or signal the show up? How exactly do you make this work? I would assume you need to use some realy bright LED's like 5,000 or higher MCD's, and put a light mist of paint and clear coat over them, but how do they get mounted and how do you smooth them?