Hi
The Epsom salt thing is about giving the plant a big boost of magnesium (which it can get in lower amounts if you're using a blooming fertiliser as opposed to a growing one). I have tried it recently as an experiment but didn't want to over-do it. So, I gave a couple of my Phals a watering with epsom salts about 4 weeks ago and nothing so far but I will do it again this next watering to see. One of the other effects is meant to be the promotion of a richer green colour to the leaves, so I'm also keeping an eye on that as well. Time will tell I guess (but they don't seem to have suffered from it, which is the important thing!!)
Oh, and you're not the first person I've seen on here to say that you can't get clear pots in NZ!