I just stained my garage floor a DARK gray, I read the directions front to back many times and it never says anything about sealing over the stain? The floor is 25+ years old, I washed/cleaned the surface with BEHR cleaner, then eched with their rust and echer, then a coat of the dark concrete stain. Should I get some BEHR concrete sealer and put it over the top? THX for the help...