Sunlight dish soap for greasy marks (just a bit goes a long LONG way on a damp rag... just tap a damp rag against the crust on the top of the spout)... and for less greasy marks and for display screens, I use the same glasses cleaning solution I use on my glasses. If it's safe for the Nikon lenswear coated specs that sit on my face all day, it should be fine for any plastic surface... (spray on the cloth, not the equipment, don't want it running behind)

Bren R.