You can see how Norbu uses the blade to gently take down the repair material, using the straight edge to help keep the contours of the shape consistent. It is our plan to use the M120, thin set, to smooth out the bubbles and rough spots of the M90 repairs. Though we are the ones who will be "teaching" anyone new that comes along to work on the repairs, do keep in mind we've just learned how to do this ourselves! It take practice and focus.