I was very surprised with The Martian, I enjoyed it HUGELY.
That's not how we do it, and you've been deeply aculturated, that's why the idea is blowing your mind. :)
I'm sure men can do differently, but I pee into a cup or a bucket, and go from there. I don't just pee *on* the plants. I can change the thread title if it helps.
If you don't store the urine there won't be smell. The smell occurs when the ammonia present begins to evaporate into the air (Oh, look daddy! There's all that nitrogen, offgassing into the air!). If you need to store it, a covered container works well.
Yes, it's an excellent source of N. How much is too much? Enough to burn. The answer really depends on the quality of your urine. If you're like me and drink a lot of water daily and thus your urine is very dilute, you're going to probably have a hard time overdoing it. If yours is highly concentrated then it should be diluted, starting at around 5:1 (I know, many if not most suggest 10:1 but I've never been able to actually *feed* a hungry plant diluting at that ratio, even using other people's urine).
Never urinate directly on the plants. Urinate into a container and then use. I use it in my aquaponics system, but it's a 1,500gal system so I can't even come close to producing too much. Even when we were getting 'donations' from the neighbors we couldn't get the NH3 levels up.