I'm not happy with my results trying to fill in the lines on the body tubes,I can still feel them with my finger nails.I've been using this red goop made by Bondo and really not enjoying using that either . I'm going to redo it today and I have 2 questions .Can I use Elmer's wood filler on the lines? I have a tub here ,don't remember why it looks brand new. Also ,should I have primed the tubes first ? and won't this effect how strong the bond is between tube and fins? Oops a 3rd question,how important is it I go out and buy a sanding block. Thanks again