Never heard of clear coat on gel. Maybe it's a RV thing not a boat thing.
Be careful about the 400 grit advice. It's not that simple.
Yes for verrrry bad oxidation one would possibly start with 4-600 grit and then work up thru several stages to polish but 400 grit alone will just leave the surface dull AND scratched.
Most oxidation will come off with a med/heavy cut compound then polish.
Oh, someone be specific please on the differences between a "gel coat specific" wax and non gel wax.
I can say for certainty that after years of fiberglass boat ownership that there is no wax that messes up gel coat. Some last longer , some get a deeper shine out of dark colors. None of them are detrimental to gel coat.