Before partaking in an act of 69, defecate in an old pair of underpants and pull them down to allow your penis to move freely. Then, as you are about to ejaculate, let the excrement flow out of your nappy onto your partner's head, taking care not to let it flow out prior.

Strategic timing and handling skill is necessary to execute this one. It's not for the faint-of-heart.
I was parked in the rest stop when, out the back, I saw an adventurous young couple performing 69. They did a Wyoming dump truck at the end; it got everywhere.
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