Unusual Tree Help Needed

I need the advise of those who work with unusual tropical/semi-tropical plants. Late last summer I ordered what I thought was to be a small trees and got a 4+ foot instead. It is a Dichrostachy's cinerea (princess Earrings, Sickle bush or Bell Mimosa are some common names). It has regained its strength and had several larger branches up high. How do I turn some of the larger branches into pre-bonsais? (cut a branch and stick in sand or water? (air layer a branch? or?) And when should I begin the process? As always your expertise is appreciated.

You could start here: http://www.ces.ncsu.edu/hil/hil-8702.html
Google is your friend ;-)

Hi Doug

If you don't mind me asking, where did you get the tree?
Looks like you are in the US, and the tree is African.

The species is invasive locally, likes disturbed areas next to roads etc.
I've tried to collect several times but failed, suckers mostly.

I'm not sure at all, but my gut tells me an air layer will work if anything does.....

I might have tried cuttings, it was my early days and I tried everything....only remember the successes.

Thanks Joseph for your response. I am very familiar with the how of reproduction and of course the excellent resource of NCSU and the great universities across our nation. I was asking for specific information on this tree. It is not common in the US and because it is invasive actually should not be used.

Gerhard no I don't mind your asking. I actually found a few bonsai dealers selling small trees and my giant was in a 3 gal pot. They are available from TopTropicals.com for about $25us. Yes I was leaning toward trying to air layer, but may just try a cutting as well. Would you suggest trying with a hardened branch, green, or semi hardened?

Thanks to both of you.

Perhaps this will provide the info you are looking for:
http://www.worldagroforestry.org/treedb/AFTPDFS/Dichrostachys_cinerea.pdf

Thanks armetisius. I had not thought to look there. Great site with a lot of info. Sadly at a quick glance I did not see any info on reproduction, other than seed pods. Thanks again.