If due to ambient temperatures you need to standardise on a temperature that is higher than 20C, a good choice might be 24C. Much higher, and you risk damaging film.
I recommend against using sponges, fingers or other aids, although it is okay to use them at the extreme ends of the film, where there is no image.
I find that Photoflo mixed according to the instructions does work, although I replace some of the water with alcohol. The dilution that works best for you may vary with the qualities of your water.
If you have the ability to arrange that the drying film is hanging at an angle (45 degrees?) it can aid in avoiding water marks.