1) Groping one's non-flexed pectoral muscle/man-boob and pretending it is a real female breast.
2) Talking/moaning in a high-pitched, female voice while masterbating, pretending it is the voice of an actual female.
3) Tucking the genitals between one's legs while staring at one's self in the mirror.
-Sick dude! I was so pumped up that my pecs actually felt like tits! It was awesome! Best narcisex of my life!