Quetiapine will absolutely work as a sedative and if you take it at the right time in your protocol, it will definitely reduce the time it takes for you to lose consciousness, it just won't help with anxiety the way that benzos would.
I would experiment with the quetiapine a little so that you know where to fit it into your protocol. Take the amount you would want to take on your CTB day and start a timer at the same time. Note down the exact amount of time that passes between you taking it and when you start feeling drowsy, and also try to note down how long it takes for you to go to sleep afterwards. That'll help you know when to take it before taking the SN.