IME Wing cabanas are usually full (although I'm mostly in HKG departures late at night or have come from my hotel and don't need a shower), and the Showers in the Wing are too hot - not the water itself, but the air in the shower cubicle due to the "hot bunking" nature of them.
The QF F lounge doesn't open until, I think, 4 pm so there's only the QF J lounge downstairs (and I haven't tried the showers there).
The QF F showers are marginally better (cooler) than the CX showers if the lounge is open.
A colleague swears that the pay in lounge has the best showers, but I don think he's tried any others and I haven't tried the pay lounge ones.
Good luck!