I already have a fine painters' tiny brush. Sometimes I use it immersed in alcohol, but it does not, by itself, do the job.
Perhaps, or better said, "unavoidable," is the use of a stereo microscope that makes the difference, Johan Ingles-Le Nobel`s site is the first site I visited, and I go there very often. I'll buy a stereo microscope eventually--it is necessary.
The use of toothpicks is something interesting.
Till now I am making the most of the cleaning process in Photoshop, but I consider this something like cheating. In one way or another I prefer to use PS only to deal with some issues of the color (increase a little the saturation and contrast). By the way, I found out that Lightroom is doing ä very decent job, too).
Thank you very much, Charles, for your tips.