The follow-up jiggle is a part of the process of male urination, usually in toilet paper-less setting, such as at a urinal, during which the male shakes all drops of urine from his penis, so as to not let them fall into his pants.
Chaz: "Bro, you've got some yellow stains on them white pants of yours. You been forgetting to do the follow-up jiggle?"
Hank: "Nah, brotha... I've been doing to follow-up jiggle. You know what they say... 'No matter how much you wiggle and dance, the final three drops will fall in your pants.'"