Yeah my introduction to Howard Levy when I was a teenager was the Bela Fleck album Flight of the Cosmic Hippo. I LOVED that cassette! I will never be able to play like Howard, but I love listening to him.
Yes, that cup technique is cool. Kinda like a plunger mute on a trumpet or a trombone. In fact, there is a product from Roly Harp called the Harmonica Wah that you might enjoy check ing out.
Rock on,
Luke