Have you tried vacuum cleaner? Use the small nozzle, or if not small enough, use duck tape and slit a small opening. Should be forceful enough to suck it out along with other debris/dust.
Duck tape!
Just kidding... Ha!
When I use manual focus and zone focusing, the shifting also occurs at times changing the distance of focus. Got to beware of it sneaking up on me.
Save to use older W126 for photos and the newer W126S for video (longer duration). The S has better heat containment technology to offset the heat from recording video for longer duration. If just few seconds clips here and there the older one should do just fine.