I have a plaster base to which I need to affix some ground cover (sand ballast, ground foam, etc). Should I just sprinkle it on the dry plaster and spray with a 70/30 mixture of water and white glue? Or do I wet the groundcover with water and dish detergent, then spray with the glue mixture? Should I add the dish detergent to the glue mixture? Thanks in advance for any help.