yes, if you were to use sandpaper that was designed for wet sanding. The problem with most random orbital sandpaper, and most random orbital sanders, is that they are designed for woodworking. Woodworking paper tends to be AlO2 and is typically bonded with a non-waterproof adhesive.

Non-waterproof sandpaper works better on soft materials like wood because it tends to "load" less, so it lasts longer.

If you hand sand, you could use Silicon Carbide paper (the black stuff labelled "waterproof"). This would minimize dust, but cast iron is very very hard, and would probably be difficult to sand evenly by hand.