The Erdnase Bottom Deal is an excellent move, and it's a great entry-level bottom deal. First, I would master the Erdnase grip before you move on, it will make the deal significantly easier. When Erdnase mentioned "in and out," he means the ring finger to loosen that bottom card by buckling it in, and pushing it out to the side. The tip of the ring finger should be against the face of the bottom card while you're doing this.
After you get the Erdnase Bottom Deal down, I recommend you jump into Marlo's Master Grip from Seconds, Centers, Bottoms. In the grip, you can do a second, bottom, center, and true deal all in one position. This is great from a performance aspect, considering every deal looks exactly the same, and it will eliminate the need to change grips for each deal.
Thanks,
Brandon Beckman
Conjuring Creations