J.;
I have not read what the other moms have done...
my son is the same way at almost four years old, but I have to say you are almost right on!
for my son I do this:
I tell him the thunder is the Angels having a bowling game in the heavens. The lightning is the strike.
I also have a deck of Angel cards (as these are always nice to have to pick up one's spirit!) and I showed him these to let him get a 'sense' of what the Angels looked like. The deck has a few child Angels. He can easily relate to children, obviously! I then let him pick any special card to hold and look at (carefully, of course!) while the storm is going on.
this helps him calm down so much! I was truly amazed how well it worked the first time. The next time a storm came, he asked for my Angel Deck. And, more importantly... he was calm!
You can also purchase Chamilla/ Chamomile ... this is a homeopathic that can soothe them, it's great for ear infections/aches and teething (of course... she may be over most of that now). But it does a lot!
When there's a severe storm, my son gets a homeopathic if the card he is holding doesn't really help... meaning he is still 'unsettled', but not really crying.
Good Luck!