I really wish I had taken some before photos of my Mistral before I started to rebuild it.
When I got it, the original duckbill had liquefied onto the exhaust can and exhaust hose. With some elbow grease, a wire brush, WD-40 (yet another use) and some time in my ultrasonic, I was able to remove it all from the can.
For the hose I used some terry cloth and WD-40 after I turned the end of the hose inside out. Hopefully the hose's integrity hasn't been impaired by the WD-40. If it has, then it is no lose, as the hose would have been donated to Gomez for his next dive.
All I need now is a couple of those fancy silicon diaphrams and a band clamp... and I think she would be done.