I can't think of any circumstances where you'd need to apply gel coat. if you have a big gouge in the glass I'd either use resin and mat, if it was structural, or body filler if it's just cosmetic. Corvettes never had gel coat from the factory, so no need to "replace" any.
The "hair" that you can get after sanding fiberglass wouldn't show up until you sprayed paint on it, but epoxy will definitely lock down any of that, should it be an issue.
Also, from your description of the old paint, I would not be a bit concerned about spraying epoxy over any of it, after a good heavy scuff, and blending any chips etc. it must be pretty dang solid if you can't scrape it of with the razor blade.
Russ