Ouch, I hate you have to suffer through that! I too wish I had heard about the mustard thingy!! I burned myself with a curling iron about three months ago. It was a 1 1/2" barrel and where the clamp or arm that holds your hair meets the barrel, there is a slight lip or ledge and this is the part that got me. Now I have a scar that looks like a set of lips (haha, hot lips) on the inner arm just above my wrist - you know, the soft tender part of the arm.
I know what you mean about the MMF as well. The first time I tried it I singed my fingers a bit - I was re-heating it to soften it up a bit. I did let it sit for a moment before I dug into it but it was still very hot in the center, still in liquid form almost. Thankfully it wasn't as bad as your situation.