I usually fly out of Terminal 1, but I’ve also used Terminal 2. I’ve been to all of the lounges in Terminal 2. That said, I’ve never used the showers in Terminal 2.

Exiting immigration/customs and making your way to departures is a little confusing, at least for me. I’m assuming you should be able to use the Sky Suites Lounge, which is very close to domestic departures. IMHO, it’s the best of the Terminal 1 lounges. Plaza Premium, which states they do have showers, tends to be overly crowded. But at the time you arrive, it might be ok. It’s a little hard to find.