Digital BW, The Print

I have some old B&W negatives that I have tried to clean with the 
usual method( de-linting cloth and air gun) , but they just don't 
want to come clean . Despite all efforts, the scans of these old 
negatives have too much junk on them to be useful.Is there anything 
else that can be done to clean these old negatives up? Any safe fluid 
they can be dipped in ???