My whole body is involved as I make the plaster by stirring and pushing sand into the lime till it becomes like cream cheese. The sand is taken over by the lime and gets lighter as it makes the bond. One trick my teacher Jose taught me is to take a tiny piece and throw it against the wall and see if it sticks as a test to see if it is ready to trowel onto the tiles or styrofoam that I use for my support. These lightweight materials make it easier than building larger heavier panels with sublayers of plaster.