Like Ian said, use a tray of the appropriate size.
If you have hard-water stains, a water wash will often not do the trick. If the streaks won't come off easily in water, try a prolonged soak in working-strength acid stop bath before the wash and wetting agent. The acid will often dissolve the deposits.
I'd likely hang using wooden clothespins, one on the top and bottom of each strip. If you're careful, you can get the pins to grip in the non-image part of the film.
Best,
Doremus