Weleda do a great range of nappy creams - it might be worth having a look at their ingredients and seeing what you can make of it. They use Calendula products, and they do not build up on nappies.

We use the paper towels in a solution of water, baby wash and baby oil. I'm sure I could change it to being more natural, but just haven't got around to it.

Will be interesting to see how you go - make sure you post back with any successes!
Fi