My technique never fails. Here is what you should try:
On the flip, raise both of your legs,so that you are in a crawling position. Aim your arsehole in the direction of the sink or shower stall. Then, with as much force as you can muster, unleash the wettest fart that you can. With training, you may be able to aim a kernel of corn, or chicken gristle right into the sink. Then, while she is screaming and trying to strangle you with a pillow, grab her face and plunge your cock down her gaping throat. Shoot your load. When you are done, give her some candy.