I am not sure how big of an area you are painting or to what color you are changing it to. Bondo will work fine followed by a primer over the whole surface especially if you plan a drastic color change. The primer will allow the paint to cover uniformly and make complete coverage easier. Depending on the contours and total area, hot dog rollers might be a better choice for applying the paint. Spray would be better for smaller oddly shaped surfaces. Unless the present finish is extremely glossy, sanding is not needed but wouldn’t hurt either.