How is best to clean metal Venetian blinds?

I like the Swiffer dusters, which come with a handle, so you reach up a bit.

Liquid Fabric softener and water

I highly discourage the Swiffer option as it only transfers the dust to the floors or furniture. Use a wet option so the dust is actually picked up and removed.

Hot water and liquid cleaner,put into a tub. Be careful you can get cut.

I used to close them and go over them with a warm rag that was dampened with a water and vinegar. The water kept the dust down and the vinegar cut the grime.