One very simple way to get them on board would be due to new changes in border security. Every single vehicle, car, truck everything will be searched and inspected. This is for the safety and security of United States citizens.
The lines of traffic would be backed from Tijuana to Ensenada.☺
And those vehicles having “contraband” would be loaded onto a giant magrail catapult, including the “occupants,” and fired off back into Mexitrash at about 500 MPH. We could make a gameshow of it - sell tickets to “push the button” ... And we’d make enough money to pay for the wall. Problem solved - that was easy.