I have used benzoin before to ease my congestion. Whenever I get a cold that leads to stuffy sinuses and a cough springing from my chest, I add some benzoin to a pot of boiling water.
As it boils, I hang my head over the pot and inhale deeply. I hold a towel over my head and the pot to trap more of the fumes. I always feel like my mucus loosens up after this.
If I'm having trouble sleeping while sick, I put some benzoin in my vaporizer. I put it in my bedroom and shut the door. That way, I get to breathe it in all night long.