When I checked into propagating magnolias the best way was airlayering
supposedly in about 6 months you will have a rooted plant you can cut off
Make a wound on the branch or make a cut,slip a sliver or something to hold the cut open,dust with rooting hormone,pack damp peatmoss around and wrap with saran wrap or that new stuff ,press and seal,then you can wrap with tinfoil for protection
I have not tried it yet
My neighbor had a huge one that I was going to try it on but I think they cut it down
I've not tried layering a magnolia yet, but I have had great success with azaleas, both native and hybrid. I just bend a branch to the ground and put a big rock on it. The first time was just a whim(did'nt even use rooting powder)and worked great. I have good luck with roses like that to. A magnolia would need some pretty low branches or suckers. Good luck!