Which preposition should be used after the noun 'skill'?

As a native English speaker, it seemed obvious to me that “skills in” was the only one of the alternatives I would use from the list above. However an internet search was frustrating because I kept coming up with the likes of “technical skills”, presumably reflecting a more common sentence construction.

Rigging my searches, I managed eventually to come up with some related examples from books, all with ‘skill’ (singular).

…during the advance on Cambrai he showed ‘skill in attack’.

Because he showed skill in managing people…

He showed skill in easing the repression…

He showed skill in the decoration of pottery…

This, of course, does not prove that the others are incorrect. They just don’t sound right to me.