Going to be rendering over the outside of some ones house - the brick is in good condition, but have been wondering about the best way to form a good key for the render - as the pointing is in good condition its not going to be that easy to knock out some of it - would using an angle grinder be a good idea? i.e. in the joints and across the face of the bricks, Don't want to be up a ladder for a week with a hammer and chisel! Also going to be using a sand, cement, lime mix. Cheers.