Paul did explain it on the tapes
Basically you use your index finger sliding it from near the center of the book towards the outer edge pulling downward slightly and this helps lift the page. Also slight pressure from the thumb as it moves up to catch the page, helps push the page up slightly making it easier to get the lift. Its a smooth circular type motion.
While the left hand walk catching the pages. Thumb is raised ready to catch the page and the index finger is holding the pages down. Once the thumb catches the pages the index finger moves ontop of the page to allow the thumb to get ready to catch the next page.
Fortunately its easier to do than describe 
Alex
