HI, I AM A FIRST TIME WASHROOM RENOVATOR AND AM STUCK ON A SPOT. I PUT DENSSHIELD IN MY SHOWER AND GREENBOARD IN THE REST OF THE WASHROOM. I AM WONDERING WHAT KIND OF MUD I USE ON THE SEAM OF THE DENSSHIED AND THE GREENBOARD. I AM TOLD THE TILES WON'T STICK PROPERLY TO NORMAL DRYWALL MUD.