Pottery, ivory, bone, or other porous decorations should only be dusted with a dry cloth. Moisture or water will stain them.
Likewise keep water and other liquids away from dolls and other cloth objects. To dust cloth items, you can put them in the dryer and tumble them on the no heat cycle for 5 to 10 minutes. The dust will come off and go into the dryer lint catcher.
As a alternative, store knick-knacks in a enclosed glass case. They’ll look new for months or even years without collecting the dust found on items displayed on open shelves.