Photo-flology:
The camera store guy was right about not using a squeegee -- sooner or later they will scratch the film. Wetting agent such as Photo-flo is a better solution (no pun intended!) The wetting agent lowers the surface tension of the water, so it spreads out into an even film instead of collecting into droplets.
You do have to be somewhat careful measuring out Photo-flo -- not enough and it won't work, too much and it will leave scummy marks of its own.
Measuring it is easy -- just buy a graduate small enough to have markings for individual milliliters, then add 2.5 ml to 500 ml of water. If you don't like measuring every time, just get a black marker and mark a line at the 2.5 ml level, then just fill up to the line.
Don't just dump the Photo-flo in the tank with the film on the reels. The Photo-flo will leave a residue on the reels which eventually can build up enough to affect evenness of development. Instead, mix up the Photo-flo solution separately. After washing, strip the film off the reel and dump it loosely in a plastic container that you've filled with the Photo-flo solution (one of those round, flat disposable refrigerator bowls works well.) Slosh it around for 30 seconds and then hang up to dry. Another advantage of using it this way is that you can re-use the same Photo-flo solution for several rolls of film.
Even if you're using Photo-flo, you still can get whitish marks from minerals dissolved in the water. As the film of water evaporates, the minerals stay behind and get more and more concentrated in the water that remains. They usually take the form of thin lines running the length of the film; they're very hard to get off and a pain to spot out. One way to avoid them is to use distilled water for your final rinse. Another way, which sounds drastic but worked like magic for me: When you mix up your Photo-flo solution, add the same amount of isopropyl alcohol as you did Photo-flo. The alcohol keeps the minerals dissolved until they have a chance to evaporate.