Many times it is difficult for folks to be able to shuffler a deck of playing cards. While the reasons vary, to be able to perform a "riffle" shuffle if often near to impossible.  The truth is, if you really want a "better" shuffle I would recommend using an automatic playing card shuffler anyway.  Not only are the cards shuffled better with an automatic shuffler, but the "riffle" shuffle destroys a deck of cards.  Not to mention if you want an "honest" shuffle you would be better off to use a playing card shuffler.