Trying to save some money, I followed the hints on the forums and used diluted white glue (about 1:1) to put Woodland Scenics static grass down on the plastic base of my diorama, instead of the pricey Woodland Scenics landscaping glue. The base is an IMEX display case, which I did roughen with coarse sandpaper before putting down a single rough coat of brown enamel paint.
I let it dry thoroughly after pressing down my mixed shades of grass to try and get good adhesion, but now big clumps of the stuff are coming off. Should I just scrape it all off and start over, and cave in and use the Woodland Scenics glue? How do the rest of you get this stuff to go down and stay down on a plastic base?