Running a Gel
While wearing a lab coat and a face mask, you pour a 3% agarose gel on your girl. You attach electrodes to your girl's nipples, and have sex with her on the gel under a UV light. Right before you cum, you pull out and cum on her stomach, revealing distinct bands of glow-in-the-dark cum.
"Hey guys...I heard last night Special K was running a gel with that new intern and made her cum four times in a row!"