Currently working on a fiberglass bodied dune buggy. Other than the original gel coat, the body has been painted once around 2016. That paint consisted of a layer of primer (definitely not a high build) and a base color + Clear coat. I've started the bodywork, correcting the previous repairs that used a regular body filler rather than actually repairing fiberglass and using a body filler made for fiberglass. The areas that need repair get taken down all the way to bare fiberglass. My question is how far down to I need to sand the other areas. I know that there's no way to see all of the potential problems without removing the latest respray, but can I stop at the original gel coat layer or do I need to strip EVERYTHING down to the bare fiberglass? My original thought was that I'd take it down to the gel coat, cover with an epoxy primer and follow that a high build primer to block it? While I don't want to waste time sanding if it isn't needed, it would be way worse to waste the sanding time, the materials cost, AND additional time to re sand because of a skipped step that causes an issue. Any guidance greatly appreciated.