It's hard to explain, you just kind of do it. You start by cutting the deck a few times into various piles, then reintroduce those to the main deck, never letting them fall to the table. You generally do this with the cards in a vertical orientation. When you've done that, and you have a solid deck again, you then cut them evenly into two piles. Then you sort of lean them in towards each other like an A frame without the lower line. As an overview, what you should have are two fairly equal piles of cards, one in each hand. They should be on the table and vertically oriented with your hands holding them up by the tops. They should be leaned in towards each other, so that the gap between the two cards becomes progressively narrower the closer to the tops of each pile you go.

Now the fun part. I will warn you that this will go badly before you start getting a hold of it. Also, when it goes badly, a lot of the times, you'll end up with cards that fall face up and face down. You shouldn't store them that way, so you'll want to sort them out again so that the face of all the cards are pointed the same way. So here's what you do. Place two or three fingers on the back of each of your two piles, then sort of slide your thumbs back the deck, like you are trying to close your hand to grab something. When you do this, try to do it a bit staggered, so you're not doing it at the exact same time. Keep working back the deck, and notice that cards are falling into the middle. Once you have no more cards in your hand, go to the pile and straighten them up, optionally cut the deck one or two more times and you're ready to deal.

It takes practice, and like I said, be prepared to sort out all of your cards when it goes wrong, because it will. It's also worth noting that new cards are trickier to handle than worn ones. They get better the more you use them, less stiff and all that.