You just have to hit the close C, f+B chain as fast as possible, and start charging d/b before the chain actually finishes on screen. Usually, I'm already charging d/b before the f+B has even come out, giving me ample time to charge it fully.
Granted, I don't do this combo that often. I prefer the close C, f+B xx qcf+D -> c.A xx EX flying kicks combo. I tend to do this in a pinch because although the link is more difficult, it is easier to hit confirm in a pinch.