I have always placed the clean negative carefully into the (clean) negative carrier and then perform this high tech exercise (on both sides):
Dry your lips completely, then as you blow onto the negative use a camel's hair brush to simultaneously help matters along. It actually works. The reluctant, clinging pieces of dust are dislodged by the brush and the unidirectional air coming from your mouth gets those loose particles going away in only one direction.
Again, it actually works, even though it is extremely high tech. Make certain that those lips are dry or you will be washing your negatives once again. - David Lyga