Advice on setting up Scheduling under client's google account

Hey gang!

I am looking for advice/best practices on setting up Scheduling for a client. Due to security codes etc., I always find it challenging to access and connect someone else's google account. Besides asking them for their google logins, and having them text you security codes as needed, am I missing an obvious way to set up and connect their google accounts?  

(Since I usually work in Chrome, I'll often try to use Safari for connecting someone else's accounts which is fine but still not ideal. So, I'm wondering if other folks have a better workaround.)

Thanks!
Rachel