I have used paypal, just not with underworks.
Everything takes up to 5 working days - transfers to / from your bank account, and the 2 small payments to verify, etc. Slow, but simple and works.
When they ship things to Australia, they do it in a small envelope for documents. It does feel like a t-shirt. It does not say "underworks" on the pack.
If I remember correctly, if comes from "Simple Solutions".
As others have said, it's really discrete.
They ship to us via Fedex, which MAY (depending on your location) get handled by AAE (Australian Air Express).
Sidenote - I'm seeing ad's on the TV lately for "forever stay up socks" by Underworks... I did giggle and wonder if it's the same people branching out to our market