Step 1) Fart a lot in her presence during oral sex and regular fucking. Do this for at least 3 months or until she gets used to the smell of your rancid bowels.
Step 2) Shit yourself during oral sex and/or while banging the snot out of the bitch. Act completely embarassed when this happens! "I agree that was awful... let's take it into the bathroom next time!"
Step 3) Enjoy your Blumpkin filled future life together.