Bonjour Clive,
Il fait exprès de m'embêter = He is annoying me on purpose
-> fixed expression / to do something on purpose
Il faut une signature expresse de mon patron = We need a formal signature from my boss
-> adjective meaning "formal, imperative, express"
C'est un lavage express = It is a quick washing cycle
-> adjective that doesn't change whether it refers to something feminine or masculine
I hope this is helpful.
Bonne journée !