Hi D. It's best to use a damp cloth and wipe off the leaves every so often (for dust), but is there a different issue you're having?
You can sit them out in the rain occasionally to wash the dust off of them or if they have big leaves, cup your hand under the leaf and gently wipe off the dust with a wet rag. They need to breath so the dust not only dulls the appearance of the plant it isn't good for it.
I merely dust mine occasionally with a damp cloth
Take a cloth and wet it with water, then just wipe the leaves, This clears the dust off and helps the plant breathe aqnd go about the natural process of photosynthesis.
I give mine a bath in the sink at least once a month and wipe down the leaves carefully.