My sympathies chaps!
Takes me back to my model train days.
I used a combination of chicken wire, rolled up newspaper and masking tape, (I had access to unlimited supplies in those days).
Rock faces were plaster faced then covered with crumpled turkey foil,(you need to remove it from the kitchen while she is not looking!), which was removed before it set.
I think your method is just as effective and great fun if you've got kids as they can all join in...
Keep up the good work.
Regards
Alan