First unscrew the red filter as it is the most fragile part of this assembly.

Remove two screws holding focus adjustment knob.

Plastic bellows are held by 4 screws on the top and bottom. There is extra plate on top and retainer ring on bottom.

You leave the metal shaft as is.

Clean all parts with soapy water. Use towel to dry. On my device the paint was stable and could be scrubbed with a brush. Degrease knob and shaft. Use appropriate chemicals to remove any other residues or stains. If you want to keep the color stable, always test any chemicals on small part that is not that or at all visible after assembly.

DO NOT USE hot water on the plastic bellows at it could distort/destroy them. If you believe they are leaking light either use some black tape for temporary fix or find a replacement.

When is everything cleaned and dry, reassemble. Replace lube appropriate for the focusing knob. Bellows are keyed on the bottom so screw that part first then the top part.