I always make sure to warm up the stop and fix a bit if I do this, too, to avoid reticulation. If I do in fact want to reticulate, I keep a container of water in the fridge, then moved to the freezer for an hour or so before developing. I then heat some water up in the microwave or on the stove, and I start developing. Perhaps halfway through development, I'll empty the tank into a beaker, and shock the film with the freezing water, followed by the almost boiling water, and then resume developing. You can do this as many times as you like, and with the fixer and stop, too.