Was it with their bare hands? I remember seeing at one of those “historical reenactment” places they used to have gloves with like a metal brush on the palms that they could use to pull the wool out.
It was just their bare hands.
That island btw was very isolated. The film was about the island of St. Kilda but the owner would not allow filming there so they used Foula which was just about a twin in every way.
The actors had to literally build there own accommodations. I believe it was shot in the 1930s.