At this point the iris can be cleaned.
I prefer to use an ultrasonic cleaner with detergent.
You can use detergent and water by hand to emulsify grease and oil.
Take care not to bend the thin bladess.
Rinse with distilled water followed by alcohol to aid drying.
No lubricant of any kind is used on lens irises.
Be careful not to magnetize the steel blades with
magnetic screwdrivers, as they will stick together.
Also, do not use ultrasonics for more than about a minute as the action will polish shiny spots on the blades if overdone.

Replace six iris blades as shown, with the down pivots in holes in the fixed plate.
Insert the seventh blade under the blade to the left and over the blade to the right.
Carefully slide the blade until the down pivot drops into the last hole in the fixed plate (hidden under the blade to the left).