Hello Angie and everyone,
No, you do use the gooey inside ... I am off out today and armed with banana skin, I am going to the nursery to ask if I can try it on a suitable plant that I should have one of (!) then I will report back to you all.
I think that the best skins to use will be 'fresh' new bananas and not when the banana is soft like you might use to make banana bread. When they are soft they are extra gooey. Anyway, let's see, I will let you know as soon as I can. Yay! A trip to the nursery - I hope I don't buy anything.