These aperture blades are very clean surprisingly. If you notice oil on the blades from emulsified grease, it will be beneficial to clean them now. The actual blades are very thin and sharp. The edges will destroy a cotton swab and you'll be left with a aperture blade assembly loaded up with cotton fiber hairs stuck in them. Use a "lint free" swab. They have a spongy material attached to a plastic stick. Soak them in some naphtha and GENTLY dab and wipe. If you wipe the aperture blades, move in a counter clockwise direction to prevent snagging on a blade edge. Cycle the aperture blades several times and use a rocket blower to evaporate the naphtha. Lather rinse repeat until all the oil is removed.