I have wondered about these ever since I got my old watch back.
I am not keen on taking the innards out of old german boxlocks as at least half the screws(and there's a few)always seem to be locked in place.
Instead I pop the assembled action into spirits overnight,then kerosene followed by the airhose,spraylube , air again,and reassemble.
This seems to get 95% of the gunk out.
But I have often thought of dropping the whole thing into an ultrasonic cleaner.