Yup, I get what you mean but *I think* there's a passage in one of the last two books where Geralt explains that he can't use signs. LOL, now I remember (I think) it's not that he can't use them without gulping elixirs first, he can't use them cause
he's lost his medallion
What? As far as I know,
witcher's magic abilities don't depend on their medallion at all...