I really don't know exactly what you're question is but here goes.
Correct me if I'm wrong.
In promenade you can move with both feet but in general just after you turned into promenade you will move out with the left foot.
When you have just done the whisk you will move out with the right foot.
Impetus left.
The problem is the is reverse Whisk, Fallaway promenade etc. And they may differ. The basic principle in ballroom is that you change you're feet on each step so if you do a whisk for example and end up with you're weight on the left foot you will move with the right.