theory11 — Magic Tricks & the World's Finest Playing Cards

Where can I learn the JW grip?

For example on volume one of Eric Jones "Metal" DVD-Series.
I´m usually not a big fan of ellusionist productions. But the Metal series is one of the few exceptions. I think they are really good.
 
Apollo robins makes great use of it in his "Whither Vanish" effect.

Shoot Ogawa (Apollos good friend) teaches several variations of this as well.

I think the best sources for (the whither vanish at least) is "Cultural Exchange" and "Shoot in Hollywood."

Other than that I am sure just about every coin book (bobo) will teach it.