About this scene
Two-person setup in a parked sedan with the windows half down. She's on her side of the car, he's on his, and she's down in his lap before the engine fan has stopped spinning. The blowjob runs long. She switches angles twice, comes up for air once, and goes back down with one hand on his thigh for stability. Right when it's about to finish he taps her shoulder and she sits up. He pulls out, she turns, and the cumshot lands across her ass through the open driver side door.
What to watch for
The pivot is the moment. He taps her shoulder once and she's already moving before he says anything. They've done this before, you can tell. The handoff from blowjob to ass-finish takes maybe three seconds and she lines herself up by leaning out of the open door. The car next to them parks halfway through. Watch the side mirror. You can see headlights pull in and neither of them stops.