after machining rotors the best thing to do is replace the pad so that they can break in together.
If you don't want to buy new pads you can sand the pads that are on now with something like 100 grit sand paper. Place the sheet of sand paper on the floor, a table or other flat surface. Place the pad on the sand paper friction surface down and sand with even pressure in a semi-circular motion until the friction pad is no longer shiny.
