If you're taking the time to clean fixtures, you may as well clean the bulbs. They only add a few minutes to the task, and all you need is a dry microfiber cloth and some water.
First, unscrew the light bulb fixture
Second wipe the dust away with a damp microfiber cloth. A dry cloth won't do the trick because the heat from bulbs can bake dust on to the surface.
Source: Merry Maids