A combination of a
gal who's an expert at giving killer hand-jobs and a guy who's so aroused dat he's just about
ready to blow when da gal first takes his tautly-engorged schlong in her hands, and thus she gets him off with just a single
up-down rub.
If a gal has
perfect timing with her hand/wrist/arm when performing a 2-stroke engine with a
virile dude, it's possible for her to achieve a "synchronized plug-firing" --- i.e., doing the down-stroke on the boy's cock at the same moment as each throbbing burst of release --- during said balls-draining session. Plus if the guy's sperm-glands are fully
recharged from having waited a sufficient period of time after his last ejaculation, then this "piston-cycle" operation can be performed up to maybe a dozen times for each successive spurt until the eager stud finally "runs dry".