When staying over with friends it's often possible to shave the night before or to get some quiet time when no-one else is around to shave quickly.
I use a Norelco rechargeable men's razor and it's pretty quiet. But usually it's possible to slip out to the washroom when others are watching TV or doing something together and give a quick rub over my face with it. Even a five second rub over my upper lip or another five seconds over my chin is an enormous help.