I picked up an important point about the taan sau when i was in the U.K.
the angle of your wrist makes a huge difference in terms of which muscles are being used.
Below is the Taan with the wrist straight, this is the "weak Taan"
Below is the Taan with the wrist angled, this is the best way...
This is the Taan- Dar idea of simultaneous attack and defense.