I’m not finding links, but according to an old Filipina babysitter, it involved tying them down, reciting prayers, and rubbing some plant on the soles of their feet. That was supposed to lead them to vomit up the chick responsible for them being an aswang, which could then be killed.

Closest I’m finding is at https://www.aswangproject.com/aswang-lore-transferring-the-black-chick/