I am tiling my bathroom using Porcelain tile. Flexbond Fortified thin-set will be used to adhere the tiles to the durock. I am currently preparing to tape the seams between the durock sheets and drywall/greenboard. The existing drywall is textured and painted. The recommendation from others was to sand off some of the texture and paint from the drywall/greenboard so that the compound could properly adhere to the drywall. How much should I sand off? Just enough to allow the tape to cover evenly on each side of the durock and drywall?