Lots of good info in this post: Awaiting Biometrics (Stage 3) - #2098 by PTbound
Basically, several people have paid successfully with foreign credit cards, everyone else with Portuguese debit cards. Though i worry that different biometrics offices might accept different payment methods, like maybe some of the smaller ones like Portimão where i’m scheduled only take Multibanco cards, who the hell knows. Sigh every step in this process involves some kind of uncertainty and worry, doesn’t it?