Satin is correct. I did mine off the car. I removed the dings and scratches, polished, and then used wax and grease remover. Wet sanded the part to be painted with 600 and then did the masking. Degreased again and then snapped them onto a board that I had screwed 2 of the plastic roof clips to. I fastened the board and trim piece horizontally to a post, with the tape on top, so gravity would help keep the paint from running under the tape edge. Be sure to use very light coats of paint. I switched back and forth from painting, to prepping the next piece. It takes awhile, but it's well worth the effort.
Dan