What I've seen and tried up till now when I process my own black and white films is either to use one of those off the shelf chemicals to get rid of water marks on films hung out to dry, or even novel ideas like putting a little amount of washing detergent into the final rinse. I've done the later quite a bit and noticed that after scanning there's stain every once in a while. They're washable but a hassle. Just today I tried to do something different, but probably what I should have done all these while. I was processing 2 rolls of Ilford FP4+ and just as I was rinsing the film and tank after the fixer stage, I thought about pouring fresh water on the film after I hang it on the hanger. What you want to do is to pour it in a steady stream, without any splashing so that the water just flows from one end at the top to the other end. I was hoping that this prevents or minimises beading and if you dont splah, you dont get pockets of water droplets that just wont flow to the end of the film.
So far so good. The 2 rolls of FP4+ that's hanging to dry right now looks cleaner than ever before and I dont even have to buy any gimmicky chemical or rubber squeegee to do that!