I believe that the method you are trying to use is to facilitate a DL???
In that case, the best thumb count techniques are the more invisible and natural type. The following is my own preferred way, but it's quite easy...
1. Hold the deck in dealer grip, casually in your usual dealer hand (mine is my left, so I will go that route here)
2. Using your pinky, ring and middle finger, support between them and the thumb-base muscle, but gently—to help with part 3...
3. Bring your index finger to the top short edge—right by the top left corner... so it's pad is on the whole of the top side of the deck
4. Line the pad of the thumb so that it runs along the left edge of the deck—it's tip is at the corner almost
5. Using pressure from the index finger and the middle finger, grip the deck firmly
6. Use the thumb's pad to simultaneously apply pressure and stroke downwards over the top left of the deck
7. With practice, you will be able to release one card at a time. the pressure of the thumb holds the break
8. I have found, after many moons of practicing, that the above grip ALSO allows you to count cards with the pinky—thus allowing a pinky break. Although, this takes rather large hands and a strong pinky!!!
Hope that makes sense
ANOTHER WAY which I find far more simple (and useable) is to hold the deck in dealer grip... use the middle and ring fingers to 'wedge' the deck towards the thumb's base... which SHOULD cause the top portion of the deck to slide, so the view of the deck from the bottom should be an angle (like a \_\ shape)
This allows you to EASILY come over with the right hand and pluck off two cards by thumbing the pile at the lower left corner. This is the way I do most DL setups, cos it's fast and is barely noticeable. Also, there is no thumb counting involved, so it looks very inconspicuous.