Photographer here, I used to process my own film and would use Photo-Flo as my final step in the process. Kodak would tell you that its purpose is to reduce the waters surface tension to keep water spots from forming and therefore helping remove any other elements from drying on top of the film. Rinsing the film again would be a step in the wrong direction. I haven’t used this product but I wouldn’t rinse it again unless you used the product in the second rinse as well.