A proposal:
What if we say the first day of every month can be used for tying up the WTS phone lines. It's easy to remember and may be a time that is more disruptive than usual. If you can't call that day, just call as soon as you can afterwards. Every month can have a theme. I suggest the theme for February can be the UN scandal. We can say something as simple as, "I'm calling to find out if the Watchtower Society was really listed as a NGO with the U.N." or "I'm calling to protest your involvement with the United Nations."
What do you think? It might not be the best plan, but at least it's a plan and can be implemented soon. I'm planning on doing this and welcome anyone who wants to join me. If anyone has better or different ideas, please let us know. We can also review things we might want to say. (I suggested the U.N. scandal, because it might take more time to prepare for topics like blood or pedophilia.) After a little discussion, maybe we can announce our plans on a separate thread.