They don't have Dan Bau in any other country but Viet Nam where it's very popular.
The pickup is a small pole magnet wound with fine coil wire. Looks like a sewing machine bobbin.
The original instruments were acoustic, but so quiet they were not often used.
Now with the pickups they sound to me a lot like a pedal steel with an E-Bow.
I just love that sound.
I also had never heard someone playing bass on a Dan Bau before so after all these years it was new to me also.
Usually they have just one string made from music wire about like a 0.020 plain.
The pick is wood and looks like an icecream stick.
As you can easily see they get the harmonics with their palm edge.
The whammy bar is made from Buffalo Horn.
I guess you could call it pull release, but there is no mechanism other than the player's perfect touch on how far to push or pull the whammy bar to alter the string pitch. Guess it would be like playing a pedal steel without any positive stops and trying to get it right!

Inlaid Star Guitar 2006 by Mark Giles. SD-10 4+5 in E9th;
http://luthiersupply.com/instrument-gallery.html
2017 Mullen SD-10, G2 5&5 Polished Aluminum covering. Custom Build for me. Great Steel.
Clinesmith Joaquin Murphy style Aluminum 8 String Lap Steel Short A6th.
Magnatone Jeweltone Series Lap Steel, Circa 1950? 6 String with F#minor7th Tuning.
1956 Dewey Kendrick D-8 4&3, Restoration Project.
1973 Sho~Bud Green SD-10 4&5 PSG, Restoration Project.