get you a body file in line air sander. We use the hutchins but you can get the cheap dual piston ones from harbor freight that might last thru 1 job.Generally da sand the roughness off then file and hand block. If lots its need then alternate between them. When all scratches from sanding run same way makes cutting much slower and uses more paper. You can pass a da over it knock out some straightine scratches and then start blocking again with quicker results.