I rooted many cuttings taken in early July in Virginia by using an outdoor mist propagation bed. Rooting hormone in a sand /peat mix. Leaves cut in half. Very high success rate. Just had to be sure the plants potted up in the fall did not have their roots frozen over the winter.
As for alternative methods, it will be a challenge to keep them for dropping their leaves and having a high success rate.
I have rooted many of the deciduous species as well. Magnolias in general are easy to root with right setup.
As a side note for native plant lovers. Not so with the Fringe tree, Chionanthus virginicus. I tried them at the same time with the Magnolias. All lost their leaves after only getting callous formation fairly quickly but no roots by the time the magnolias were ready to cut off the mist.