Universal Heliar - Soft focus mechanism servicing

[mhayashi]

Hello, Steven and everyone with universal heliars.
I’ve got an universal heliar and am trying to clean the element surfaces in between the front element and the middle one.
My sample is pre WWII but not the very first one without “universal”.

I removed the rear element and the screw on the side to control the aperture blades, then what’s the next step?
Do I need to remove the aperture ring as shown in the pic?

Thanks for your help!