I painted everything except the smooth sections under and behind the bulbs themselves. All other chrome parts of the housing are purely for looks. the brightness is the same for the headlights. As for the blinker, i painted everything in front of the clear reflector that houses the blub. Those are not as bright, but are still very visible even during the day.
You have to use a heat gun to take apart the lights. Run the gun along the seal between the clear and the black housings untill the apoxy becomes tacky, then pull the lights apart.