So I am wanting to render on top of the decorative yorkshire stone wall as shown in picture, because the surface of the wall is at all different levels I need to first grind all the high spots back, question is, what is the best product (base coat) to fill it out the wall level before even attempting to apply beads? The motor between the stone is set really far back in some areas so would require quite abit of filing. Once the wall is flat I will then apply a top coat of either Weber or ecorend. Cheers for any help.