Use a toothpick to put lots of lines in the waterfall. Run lots of vertical creases so it looks like water flowing. Make some spares in case something happens, make a few extra ones. Once it is dry you can peel it off the wax paper. The caulk is a bit flimsy and it won't hold up well so just cut a strip out of a 2 liter bottle. Make the strip about the width of your desired waterfall but make the lenght several inches longer. You will trim the length when ready to install it.