Well now, personal experience over many thousands of negs, both 35mm and 6x6, may frighten the cojones off some of you, but what I did was this: lay the negative, emulsion down, on top of some clean white card (the back of olde worlde WSG) and hold it firmly by the edge of the rebate so that it canīt move; breath on it from a safe but close distance and, with the fleshy bit of your pinkie or ring finger gently rub the negative away from you in one direction only. It will remove any signs of drying marks (I did use wetting agent dips after washing) and, in all those years, never a scratch. In extremis, touch the outside of the nostril with the same finger and the natural oils there will clean intransigent material away when breath fails to do the trick. Should you get sputum on the thing, youīve just effed a negative, so be careful.
Once in the film holder, I used a fine artistīs brush to remove any dust that was visible under the oblique rays from the enlarger.
The technique above also works well when cleaning transparencies for mounting.
Sound too violent? Perhaps it does, but then I always took care of my hands... Perhaps I should employ an emoticon - nah - but possible squeals of anguish in response apart, I never did suffer negative damage with the method.
Before doing this on something that matters, try it yourself on a scrap bit of film to check out the state of your fingers and/or oils!