I try to dive places where I can get by without wearing a wetsuit but when I do and I do pee this helps me feel better. I first flush as much as possible by stretching my collar and scooping water in. I then go inverted and stretch my suit over my regulator while exhaling letting bubbles flow through my suit exiting out of my ankles. This might not help anything but it makes me feel better. When I first started diving I didn't understand what the separate rinse tanks for wetsuits was all about.
Wow! Is this the Warhammer for #1? Admit it, you just like the feel of the tiny bubbles racing across your private parts.