painting the plastic fenders and nose

[dzltek]

Just as the title says, I'm going to be painting the front of my car in a few weeks and I'm curious. With the nose and fenders being flexible and susceptible to expansion and contraction, do I use a adhesion promoter mixed with paint, or spray it on the pieces then paint over it? Or do I spray adhesion promoter and mix a flex agent in the paint? This is my first time painting plastic and I guess a poly nose.