You warm up the way your are supposed to outline in the sticky, or beginners routine.
I usually use hot towel wraps for 5 minutes, and then hot wrap for 3 minutes in between sets.
Then I end the session by dipping my penis in a hot cup (44oz) for 5 minutes.
It is loud, because of the water running. But, I have my own room/ space, bathroom, and privicy.
As far as doing PE in secret, while sharing space with others? I have no idea. Maybe get up after everyone is asleep?
But I do know that you cannot neglect the warm ups. That is how you get hurt.