Lots of good sources listed here for sure, can't go wrong with any and all suggested so far.
Two thoughts that I think are very relevant and weren't mentioned though:
Jason England is of course incredible and a real modern cardistry master I've studied from relentlessly, admire to the ends of the Earth, and he always has something to add even if you already know a sleight or move. However, as you'll notice, his hands appear to be gigantic. For learning a bottom deal one may find Jason's tutelage a bit frustrating if first learning this move in particular simply because his hands are large and GE doesn't really address this. Definitely a must-view and learn, but...
Daniel Madison's handling and thoughts on the bottom deal were unmentioned. I REALLY like his handling, thoughts, and philosophy on the bottom/Greek deal, and grip in general.
In particular he addresses the grip in a slightly different fashion, and his specific attention to detail on how his approach avoids "knuckle flash" common with the bottom deal.
The DVD set "Mechanic" contains a section on the bottom deal and is a fantastic reference to add to your study materials to be sure.
You'll find Madison's approach on this is unique and very helpful in a broader sense. He also points out, importantly, that to perform these sleights, you will eventually make them your own; your own grip, your own subtleties, your own handling, without compromising the sleight.
Honestly, a bottom deal is a bottom deal, and Erdnase, Marlo, etc, are all amazing, but really use generally the same technique. I found Madison's adaptation and deviation from the norm on grip and technique VERY helpful, and apply directly to real world situations, and in a broader sense helpful with more than just the bottom/Greek deal.
Best of luck on your journey and keep at it, when you get it you'll nail it.
