The 2 card system for VISA promos is very easy once you know what to do.

-During checkin, give them your AMEX/Giftcard and tell them to swipe it for the room & tax total.
-Then have them swipe any visa for incidentals.
-Pickup a candy bar / snack from the cabinet and add it to your room

This will charge the $1 candy bar on your visa and close out your bill to Visa and count to the promos.