Hey Robbo,
yes when I start sanding a kit I use an orbital sander to get the bulk of the machine marks off, then go to a 240 grit and auto stores sell 320 grit papers. Then I move onto hand sanding as the ROS will leave some marks if it digs in on an angle. Keep the ROS flat as you can and lower speeds. If you have a vice to put the body in that's a plus as you should be operating the ROS with both hands