Well for a long time I did all my buckle bottom dealing without the left thumb action. It looks significantly better with it, but with proper timing can still be invisible without it. The timing being that the card gets buckled out at the exact moment the right hand "strikes." The key to true bottom strikes is the left hand grip, and the direction your right hand attempts to take the card. You have to ensure that their is no resistance from your hand or the deck on the bottom card, which is achieved with tight but delicate grip, and by pulling the card directly to the right or even down. A nice advantage to mastering the right hand removal for strikes, is that you can negate many of the telltale noises of bottom dealing.