How do girls cum

Not sure what you mean by this but it is an orgasm and nothing really happens other than perhaps some moaning

What comes out

Shouldn't be much of anything coming out in most cases. If anything does come out, it is very debatable what it actually is. If you are referring to "squirting" I think that is like 5 million times more common in JAV than it is in real life. And even what that substance is in JAV is hotly debated.

How long does it take

Long enough that you may as well stop wondering how long it will take and just settle in to the love making. I invest anywhere from 2 to 15 minutes of just trying to make her feel good and then the magic happens