That's about it!
Differences to my approach:
Important! Use a heat shield of some kind for the plastic parts like the connectors and the speaker (Kapton tape, fr4 board, small wooden board, whatever)
In my case I had luck. The speaker melted a bit and deformed. But in a way that it's not so annoyingly loud anymore :)
BTW: Trinamic offers samples to companies free of charge.