The 挑打 (Tiāo dǎ) is a very fundamental part of the 八卦砲捶 (bāguà pào chuí). Better practice more. See how.
Keep the mapo, move with it, and …
The hit target is decided when the arm is close enough, not when start to move. See how
The movement and structure is defined by the joints position, concentrate to them! The next 4 video all related.
What kind of step will be the next, when stepping down we arrive to that one. The change does not come after the step down. This preparing the next movement, which can be faster. This is also a fundamental rule in Baguaquan
HeJingHan BaguaQuan, Baguazhang Teaching Taipei.
See more videos at Youtube playlists
some materials could be added from HeJingHan book:
Bagua Quan Foundation Training