After the last few weeks in outrageous lines at customs, I have decided to get a CANPASS. But I'm a bit confused...

It says you can mail in the application, but asks where you would like an interview. The CANPASS site is unclear on the interview portion. I assume this is required. After you mail in your application, do they schedule an interview for a later date once they have made sure your application is okay?

If you go in person, do they do the interview right then, or do they schedule for a later date?

Also, I assume that you can go to the airport and do the interview even if you aren't flying out (it's not past security or anything like that, is it)? Because given their hours, I'll have to go in on an off day.

Thanks for the assistance!
Greg