Wait wait wait...
I've never been able to whistle, even with the finger approach. I think it's because my lower two front teeth are inconveniently crooked, but I could be wrong..
Do you have a link or three to share for finger whistling, or any whistling for that matter?
Anyways, back to your question, I finally halfway learned the Rubik's Cube, but only after I added dice dot holes to it. Honestly it creates an interesting crossover of puzzle/die patterns.