On the third brake light, I'm interested too. I want to clean mine.
On the c-pillar, if you're a coupe, there's a torx bolt behind the light holding the pillar on to the steel c-pillar. Careful you don't snap this! On sedans, you can pull the c pillar panel right off with your fingers (no torx bolt holding it on)
As for the light, just carefully use a flat blade screw driver to lift on the bottom edge of it. Carefully. thinner the blade the better. The light just pops off and back on with a spring. after you remove that torx bolt behind the light, just pull the panel hard with your fingers. Fully pop open the window and pull the felt trim off the area you're working on.