In the same way that yin yoga can be beneficial for women hoping to conceive, we can use yin yoga to help men become more fertile and virile. I highly recommend you check out this post on yin yoga and fertility for some insights:
http://www.yinyoga.com/forums/viewtopic.php?t=480
As stated in the above post, focusing on the Svadhistana (the second chakra) can help stimulate energy flow to the reproductive organs. Any yin yoga flow that works the Kidney lines will help with this. Also, because stress can interfere with so many natural functions in the body, including our sexual organs and prostate function, just doing any form of yin yoga will help to turn off the "fight or flight" system of the body, the sympathetic nervous system. While you do your practice, attend to your breath and allow yourself to sink into the flow. Your stress levels will drop, and your natural rest and restore function will take over.
Here is a suggested flow for the Kidneys, (check YinSights for a description of the asanas:
http://www.yinyoga.com/ys2_2.1_asanas.php)
Sitting Meditation - tune into the breath
Frog: start in Child's Pose, then move to tadpole and then into the full frog
Sphinx
Seal
Saddle
Straddle
Caterpillar
Reclining Twist
Shavasana
Good luck!
Bernie