I use the same theory my mom used with me. The thunder is God moving his furniture around. The lightning is the angels taking pictures of us. The rain is the tears of Jesus seeing so many doing bad things.
I don't have kids but i think that the lullaby should work.I did that to my nephew and it worked,its not just about the lullaby but how you do it looking into the eyes and he or she sees how safe he or she is right there in your arms.