Hi
I have several Desert Roses, which I was given by a lady at a hydroponics shop in the suburbs of Perth. She had lots of babies growing in a hydroponic solution with vermiculite as the medium.
The Desert Rose absolutely HATEs having its feet wet for an period longer than about 2 days. If they do get too wet the roots will immediately start to rot and you will then notice the stems and the body of the plant going soft and eventually dying.
I have mine in a 2 types of mixtures: one type is comprised of 4mm round gravel pebbles (available from Hydroponics stores the Big B only has larger sizes) and some (very little) sphagnum moss; the second mixture is comprised of Akadama and a small amount of sphagnum moss. I have found the sphagnum moss keeps sufficient moisture in the pot and limits the times you need to water.
I would be inclined to repot at the the beginning of spring, and as the plants flower around November/December, I would wait until after flowering to prune the plant.
Also, given the very softness of the branches, I think styling by clip and cut, rather than trying to wire the plant would be best - that is what I do.
As mentioned in the thread to the post referred to below, in Perth water, every second day (if they need it) and in winter move them to a warm spot away from the possibility of frost and give them a light watering every 2-3 weeks. Fertilize as per normal bonsai.
There has previously been a post on Adenium Obesiums and my reply to that post is at
viewtopic.php?f=104&t=804#p82364 . You will also find some more excellent information there as well.
Good luck
Michael
also, here is a photo of an Adenium that Jerry Meislik took in December 2009 at the 3rd Asia Pacific Bonsai Friendship Federation convention in Bangkok, Thailand. (referred to in the thread)
Will eventually put them in a bonsai pot, once I've grown them to the style I want, as I'm not keen to use any wire on them