Im going to attempt to make a spray foam background for one of my tanks using this how to: http://www.ehow.com/how_6389304_make...ackground.html. the how to doesnt really say what kinda of silicone to use except what colors to get. i picked up a few tubes that you use a caulk gun to apply, is this the right one? do i just squeeze it on, then smear it over the foam?