Ok, fast and organized. IF you are using an electronic coupon from Alamo, you can check in online, if you are using a coupon from anywhere else, you cannot check in online. If you are using an electronic coupon from Alamo, you can checkin online and then use the kiosk you can even add your additional drivers at the kiosk.
The fastest way, by far, is to use the kiosk, go to the garage, select your vehicle and go to the exit booth with your license, contract from the kiosk and credit card you used ready for the exit booth agent to verify. If you add an additional driver, you will need to have that person and license with you to be verified.
Online check in is great, you can check in online, go to the garage, select your vehicle and go to the exit booth with your license, print out and credit card. The exit booth agent will process the reservation there, exactly the same way the counter agent would, only this way you are in your car with other cars behind you.
Thursdays are usually pretty busy days/nights, but, do either the online, kiosk, or online and the kiosk and you will be well ahead of the game.
Hope this helps and was not too confusing.