Sweat equity into an abused beachcat. Been there. Done that!

You will become very proficient with gel coat finishing, Grasshopper, which can be very rewarding once you get the right equipment and practice. The brown/tan stuff looks like epoxy that is a repair from beaching and colliding with another object(s). If the tan epoxy is sound, fair it out with something like West Systems epoxy and build up the worn spots. If you are really compulsive, grind/sand off the tan epoxy to see what really lies beneath. Thereafter, shoot some gel coat. Goes on heavy (20mils?) per coat and requires prep sanding (150 grit?)to achieve a mechanical bond. I prefer to use non-waxed until my final coat to keep it tacky during build up via chemical bond between coats (I prefer 3 for you project and about 20 mins between coats).

Let it cure well (1-3 days depending upon humidity and temp). If need be, sand off any drips after curing with 220ish. Quick wet sand with 600 and then the magic. Rough cut polish (its like tooth paste consistency) with an electric grinder and buff wheel. Followed by regular marine polish with grinder and then hand paste wax and electric buffer.

I'll defer on boards.