In the early 20th century Charles Harrison was a vocal and much respected member of the The Magic Circle. He often published his methods. Back in 1935 Harrison detailed his technique for making Cards Across play big and strong. They are worth studying today.

Note that for Harrison, at least in this trick, it's less about the physical technique but more about the illusion of freedom left in the minds of the audience.

After this, the audience will believe the Magi can do ANYTHING.