Lots of info out there on the web, but not a whole lot of detail at a quick glance. Seeds seem to be OK for the species, otherwise the recommendations are for semi-hardwood cuttings in late summer, or for layering in spring. I suggest you do a web search, and see if you can find one of the info sheets put out either by a commercial grower or one of the ag schools.
I wish I could grow durantas here, but decided that since there are toxic parts, I couldn't winter them in a house shared with 4 cats.

This is probably one of the easiest plants to root. I rooted both the purple blooming one and one with varigated leaves last fall. I probably had 90%+ luck. Just cut limbs off, cut into 6 inch or so pieces, dipped in a cheap rooting powder, put in damp potting soil, covered with a clear top and waited. I had a limb of one of my plants broken off a couple of weeks ago. I took it into the greenhouse and put it into a cup of water. I potted it up yesterday as it had already formed 4 good size roots. I would say after this experience that you can also root in water.

Patsy