The wet trades make a mess that is detrimental to other materials. There are ways to keep the place clean.
You will need builders poly, rolls of gaffer tape (Bear) and a can of spray adhesive
Clean the concrete with a garden blower. Now spray the adhesive as a strip against the wall and then bed the tape into the adhesive. When cutting the tape try not to tear it as this will stretch the tape and it will shrink back in a short while, breaking the bond with the glue. Use scissors to cut the tape.
The adhesive on the tape will stick to your finger tips, this will make it problematic to tap the tape into the glue. Using a brush or paint brush to tap the tape into the glue. Do this to all the walls being plastered. Now lay the plastic out and tape that to this wall tape.
Leave the plastic in place for the duration of the job then cut it away with a Stanley knife and buy the blades in bulk. How clean the plastic is will be the factor in how clean the cut is.
While the render is not applied to wall the plastic will be susceptible to water and wind damage. Trying to keep the plastic in place requires flat boards or planks. Mud boards, cement sheeting and lengths of steel to name a few.
As the render is ruled off and the droppings build up, you can push them into a pile along the length of the wall which also can help with the wind and water problems. A back of a small broom works well when it is still green.
Brick paving is best done by removing the border brick and laying out the plastic and putting sand out of a bucket onto the plastic edge. Bear in mind that the header brick will have to be cut to fit back into the gap.
Protecting two vertical walls like this granite wall intersecting with a brick wall requires a different approach. When buttering the brick you leave off the mortar that is wiped across vertical face arris as to minimize the mortar right in the corner. When you remove the profile scrape and clean the perp out so that a length of plastic will fit in the perp about 10-15 mm.
Then put the plastic into the perp and point it up making sure to get the plastic pushed tightly against the stone walls face.
Also because of splatter over the course of the job it is a good idea to bring the plastic up the face of the wall.