Use enough to cover the entire area with a thin film.

These were at times covered with a thin film of ice.

Think about a very thin film of oil floating on water as an example.

The board is thrown across a thin film of water.

A thin film of recent mud was left upon his skin.

There was a thin film between Hansen and everything around him.

A thin film, usually of a plastic material, is used instead.

This was now covered with a thin film of ice.

Leave a thin film of the medication on the skin.

And the water crept over the floor, a thin film of it.