How to apply wind directional source to character clothes?

I saw several tutorials teaching how to make a flip flag using wind directional source and cloth brush.
Unfortunately , none of them mentioned that how to apply this wind feature to the character clothes.
I tried by myself, but the clothes was just stick there no matter how big the wind value was.

The flag is quite simply however the clothes is sharing the same skeleton with character mesh. Maybe this is the reason?

I’m totally at sea right now…