Yes. A developed negative can be re-wet and re-rinsed to deal with drying marks, as long as you handle it carefully.

Make sure the film is submerged long enough to become fully wet again, then dry it the same way you would after normal processing. A final rinse in a wetting agent such as Photo-Flo is appropriate before hanging it to dry.

The main risk is not the rinse itself, but drying the film in a dusty environment. Dry it in a clean, still-air space so dust doesn’t settle on the wet film. Hang it somewhere with little or no airflow, and leave it undisturbed until fully dry.

So, in general: re-wetting and using Photo-Flo is fine for a developed negative, including one that’s a year or two old.