FYI, I asked the BF Conceirge in EWR to hook me up with a pass to use a shower facility when I arrived in HKG to transit onward to GUM.

She told me a HKG-based conceirge would hook me up with the appropriate pass on arrival.

Sure enough when I got to HKG, an agent greeted me at the door with an envelope that had my pass to the Premiere Lounge near gate 15 (near where transitting passengers resurface at the airport.) The lounge was tiny ...but it had a nice private bathroom and shower that did the trick. They also had a small area (maybe room for 6) to connect their computers and had a light snack area of juices/liquors/sodas/noodle bowls/nuts/chips.

After I refreshed there, I went duty-free shopping in the terminal ...and roamed over to the Dragonair Lounge upstairs. There were no longer any signs on the door that showed they were a CO-partner lounge (actually, all they had on the door was "Dragonair - By Invitation Only"), but when I asked the desk agent if I could enter, after a quick call (to CO I presume?) they let me in. While the Dragonair lounge is large, it doesn't have rest rooms or shower facilities ...but does have abundant seating and a larger snack area with a broader selection of liquor/soda/beer/juice and more upscale snacks like sandwhiches and fruit platters. (I usually go to the Dragonair Lounge when in HKG, so I decided to try it again this trip.)

In EWR, the BF Conceirge told me that CO uses 2 arrivals lounges --one for HKG arrivals and the other for transitting passengers. I didn't ask where passengers disembarking at HKG go.