fiberglass hood re-paint

Sanding it all the way down is not the way to go. I'll consult with a friend of mine who does this for a living, but I'm sure he would agree.
Yes you wanna sand it, but not to bare fiberglass. Only sand it enough to rough it up. Use 320 grit.
You can then repaint using a automotive primer that is designed to fill the imperfections. After applying that stuff and letting it set up good, you resand and prime until you are happy with the results. You wanna get down to a bit finer grit before the final finish is applied.

The only reason I would remove all of the paint is if it was peeling.