Here is very short guide on accessing aperture chamber of Voigtlander 50mm F1.5 Nokton lens Leica M mount version.
Picture below shows pieces removed in a left-to-right order: mount ring, frame ring, securing ring unscrewed CCW, rangefinder transmission ring, three metal shims.
I’ve removed these parts while seeking for option of screw out rear glass module. At this point it become clear that you need to use spanning wrench at points marked in green to unscrew rear module in CCW direction. You can do it without prior removing of all that mount rings parts.
NOTE: do not unscrew the most inner securing ring – it is holding rear glass element, unscrewing it will loose whole optics inside rear lens module. Apply spanner wrench at exact green arrows locations – it’s ring second from the center.
After unscrewing rear glass module you will have access to the aperture chamber and inner glass surfaces, where small dust particle may migrate over time from the aperture mechanics.