I've done some wiring on a large portulacaria, I definitely recommend aluminum verses copper, and going very slowly. I've never done extreme wiring, because I do consider them mainly a clip & grow specie. But I have had success in slowing working some branches into more horizontal positions. Like any other tree, when the wire is off it will try to revert to vertical growth, but a few wirings can help. I don't think you'll ever success in getting really twisted branches through wiring, I've mainly concentrated on lowering vertical branches. Let them dry out a bit - that will help relieve some of the turgidity and slightly decrease the 'snap' factor, though they will still be very easy to break.