The surface flashes over and dries in a few minutes under "normal" conditions when the plastic headlight is suitably warm. It actually takes several hours to CURE (completely harden). On mine I shut the headlights off after about twenty minutes.
On a cool day, it also helps to park the car so the headlights face the sun. One would not do that on a hot summer day, though.
On a cool day, it also helps to park the car so the headlights face the sun. One would not do that on a hot summer day, though.