A unique sex needing advance preparation and a girl there is a constant want to see once more. Before sex, get a condom and fill it with every bodily excrement possible. (i.e. shit, piss, vomit, snot, perspiration, cum, saliva, which diarrhea fluid shit). Tie off the condom like a water baloon, and stash it someplace close to the bed where it could be discreetly achieved. During sex, switch to doggie design, and merely as you sperm, break the condom over her fucking mind!