1. Use head thrusting to completely envelope entire penis.
2. Giver uses nose to draw imaginary figure 8's in pubic area.
The result is extreme pleasure for the receiver via extreme stimulation of the entire penile crown, unattainable by simply head thrusting alone. (Chicken Necking)
Can probably also be done during irrumatio, if both giver and receiver are well attuned to each other.