Plumbago pruning

I have a plumbago (3ftx3ft)which has hundreds of branches intertwined all over, is there a specific rule to how to prune a plant like this, ie. leave one main leader and let all the branches come off that, then cut them to 2 or 4 leaves, should there be a framework of 2 branhces or more, or do I just remove tips from all over. Any ideas?

 

I had a plumbago wilmotii which I pruned every march down to about 2 buds from the ground, it probably depends on the type of plumbago you have though.