Itchy Ghost Dust in second-hand harmonicas

bernd,
The most common problem you would encounter if you were to soak your harmonicas in water would be the comb swelling.
Hohner uses pearwood which is vey prone to swelling if not properly sealed, which unfortunately the older models are not.
I work on harmonicas on a near daily basis if I HAD to try to clean one without disassembling I think I would use a mouthwash like *Listerine. I would quickly pour it through the instrument and just as quickly use a hair blow dryer on low to dry it out to avoid the inevitable swelling.
Working on your own instruments is not as difficult as one would think. With a minimum of a few proper tools you can achieve some very nice results while getting an education as to how the instrument performs the way it does, and how to make improvements.
I must add that the *Listerine trick is one I read about years ago for chromatics and should be preformed with the holes facing down.
Regards, Pete

Oops...I've forgotten to answer.
Thank you both for your advices! I've watched Rex video and I will
try the brushing method on one of my unfavorite harmonicas. I recognized
that the problem gets better with my Echo Harp since I play ore often
with it...I would call it lung-filtered cleaning.
I didn't know that the Echo Harp has tiny little nails in it, my Echo
Harp has a single slit on the head of the screw/nail.
Rex, if your Echo Harp has the same, I would dare to pull them out.