As you go down on him, look him dead in the eye and, as calmly as you can, ask him: “Would you like to try and fuck my ass?” as you slowly but surely stroke his wet, and surely now throbbing, dick. and wait for the stammering “Um uh er o-okay?!”
I dunno man, but it worked on me.
DEAD IN THE EYE
As a girl, I can confirm that this works extremely well.