Where did Andy learn to silkscreen?

Buried in a New York Times obituary titled Floriano Vecchi, 84, Publisher With Literary and Artistic Bent, Dies, is this interesting tidbit:

Mr. Vecchi was born near Bologna and came to New York in 1952. He and a partner, Richard Miller, opened a successful business, Tiber Press, the next year, and Mr. Vecchi operated it until 1977. Together with Daisy Aldan they also started a small literary magazine, Folder, which became a vehicle for young writers of the period.

...

Mr. Vecchi may have left another lasting impression on the New York art scene in 1962 when Andy Warhol visited Tiber to have a screen made of a dollar bill he had drawn on paper, the first of his United States currency compositions.

According to Riva Castleman in the June 2004 issue of Print Quarterly, Mr. Vecchi told Warhol to redraw it on Mylar for refinement and instructed him in the screen-printing process, which Warhol promptly introduced in his studio, passing it on to Robert Rauschenberg as well.