Quite interesting how the Foley people look at the designs of the objects which they have to make up noises for and think of what objects will be good at conveying that noise.
In this clip, they talk about the flying hover things which have blade like spinny things, they used knifes for the sound. they tried sharpening them to make a good sound then they enhanced it to make it work.
In the Foley exercise we did, are team had an unknown sound which we had to think of a noise for, we had no idea what to do for it.
The unknown sound was a chemical reaction in a test tube where the light in the reaction glows, so we thought of a light humming as it glowed. I brought in my harmonica which makes the same sound we were looking for and it worked well, so we used it in the final clip.