Classic throat-fuck.  Grab his hair with one hand and the back his head with the other, and start thrusting like you would if you were giving it to him up his ass.  As big dicked guy, I usually have to show restraint with my partner, though.  Similarly, although I am well-trained out of my gag reflex, and I can swallow a big dick, being throat-fucked by one can present a challenge.