The idea of using papier mache was not mine, Andrew Downie from the Edinburgh University Physics Department raised this idea and he therefore deserves full credit for it.
I followed the recipe I found here. There are some more tips there, so if you want to do it yourself, go look there as well.
Here are a few photos of the papier-mache production process:
Once it has all come apart, you have to drain the water out of this disgusting soup. A standard kitchen sieve will do, but you will have to use your hands to squeeze the remaining water out of the paper, just dumping it in the sieve won't do by itself.
Next step: mix it up!
Mixing in the other ingredients is very straightforward, but I made some pictures anyway: