To you parochial girls out there, feel grateful today. For I, the wise and friendly one, decided to educate you girls a bit about the anatomy of a firefight. *firefight = a verbatim translation from the Hokkien slang of “Kew Huey”, which means “Taking a Piss”.
Now, why 2 hands ? First, please peruse the illustration provided below.

Note:
I’ve replaced the picture of the serpent with a fire hose to conserve the family-friendly rating of this site of mine.
As you can see, our wiener has the characteristic of a shapeshifter. A shapeshifter is something that’s able to fucking change it’s shape. Usually, our dicks will be flaccid just like any harmless dormant fire hose at it’s default state. But when you rub it or provoke it with something soft and warm, it will transform into something scary that resembled a really fat snake with bloated head shaped like a chicken’s ass. (I’m very sure most of you girls know about this. If you don’t, go find a nearest toilet bowl and … )
Yes, I vehemently believed that this is pretty much the basis of how Incredible Hulk was originally innovated. A normal sized organism that would spontaneously transform into a gigantic monster when provoked - oh… the resemblance. The only difference is probably the color. A dick doesn’t turn green in it’s monster mode.
So much for the introduction… now back to the topic. Usually, when a guy goes to pee, his dick should be flaccid as mentioned. He first has to unzip his barn door and use his left hand (assuming that he’s right handed) to pull down his underwear’s elastic band. This will unleash his serpent from it’s hiding place, ready to drain out his bladder content.
Being flaccid like that, you can imagine that it’s very hard to actually control the stream of urine right into the urinal (or any target) without assistance. Just imagine it like a fire hose jetting out high pressured surge of water without it’s firemen. It will just flutter everywhere soaking everything wet in it’s path. Now, nobody would want that type of cataclysm to occur in front of the urinal.
That’s why, we’ll have to use the other hand to hold the serpent to carefully control the torrent of gushing urine so that the pee could be delivered to it’s desired destination. Like, into the mouth of a thirsty housewife. Kidding.
That hand plays a very important role in complementing our marksmanship (Guys are known to have the uncanny urge to shoot something in the urinal while peeing, like a strand of pubic hair, dead insects or blotches of unidentifiend stain) and hygiene. The word “hygiene” was mentioned because we have to shake off the remaining drops of urine from our dork with that very hand. (Quote from The Hot Chick - “Remember, if you shake it more than twice, you’re playing with it.”)
So, it’s one hand holding the underwear, the other controlling the hose. As simple as that. (It looked like we’re holding our kkc with both hands but, now you know it’s not quite the case…)
You’re now bestowed with the knowledge of taking a leak with a dick. By now, you should already know how to whip out the serpent, piss and shake the remaining droplets off without too much complications; should you ever be given a functional dick.
You’re welcome.