Are there any known references on professional whistling out there? I love to whistle, but I feel like it's not very pretty the way I do it and would like to learn from a professional the best way to do vibrato, increase my range, change registers quickly, etc.
If you want to see a good example for real "palatal" or "roof" whistling with open mouth , search for "palatal whistling " on YouTube and see videos of Thomas Molnar (my own performance).
Many think , it is something miraculous. IT IS really NOT.
The key is the completely different way of creating whistling tune. Instead of rounding lips and press the airflow between them (causing resonance outside the mouth) the airflow passes the bent-- up tongue left and right and crosses before the front teeth within the mouth , creating a smooth- sounding whistle tune . Moving the lips (narrowing and widening it ) regulates the pitch of the tune.
Of course I use the "traditional" technique too for lower and higher pitches ,too - I can even breathe in during whistling so there is no need to make pauses or interruptions during the performance(see. Marcia Alla Turca)
From one of the videos you referenced:
Wow, Geert Chatrou is really something. After some research, it appears he collaborated with the makers of this documentary:
... which might be a good resource, and seems to contain some information about how to do palatal whistling.
I have a feeling that, while there may be professionals that would give you advice, you'd be as well off simply practicing different techniques and mimicking. For example I whistle on an inhale in the mid-high register for more volume. I'm sure that there are as many techniques as people whistling.
I have a hunch, however, that if you practice isolating harmonics (such as in harmonic singing) it may improve your ability to ascend/descend quickly/cleanly through the registers.
Just two cents (okay, maybe just one) from a strictly nonprofessional whistler.