In the true fashion of the Dirty Sanchez, you wipe the sweat and funk off of your cock and balls; then wipe said funk underneath an unexpecting guy or girl's nose, but above the upper lip.
The two part act of sucking semen out of the anus with a straw while maintaining enough of a vacuum to get the greasy, and sometimes chunky duckbutter that runs along the taint.
Being careful not to miss a drop, and priding himself as a pro at Felching For Duckbutter, Gabe Athouse aimed his straw and inhaled every last drop of the load he left as well as the grimy, nutsack buildup.