it depends on the casino to set a procedure for a shuffle, tHey all can do it difrently, a standard poker deck shuffle has been the same every place I have worked over more then 30 years, and when out playing I have noticed it is the same. it is cut the deck in half riffle both sides together, strip the deck doen and riffle once or twice more. cut the deck than deal. the numbers of riffles vary,, between 1 or 2 after the strip, the dealer may vary slightly, at a customer's request for another riffle or two. a couple other procedures are that the dealer should keep the deck flat on the table surface and push the shuffled half's together from the end of the deck without covering the the top the deck A procedure more often ignored then not. most dealer are not awsre og it Or not practiced enough to do it without cards going all over the place, the dealer should not bride the deck and when cutting the dealer should use only one hand. You asked about multiple decks, which poker never uses, that is a Blackjack thing with more than one deck, I doubt you will get an expert answer here, I have dealt 21 and all I can answer is yes there is a procedure, I just don't know what one might be.