I would try wet sanding with 1000 grit paper. You'll know pretty quickly if you have enough finish left. Buffing does the same as wet sanding, it removes very thin layers of paint. In my experience, unless you're very experienced with the buffing process, there's a greater chance of buffing too far into the paint. Wet sanding with a fine grit paper allows for more control.
I've redone a couple of old Checkmates with metal flake. Early metal-flake glass boats are very difficult to bring back evenly. Whether you wet sand or buff, it's very difficult to end up with an even finish. Especially topside. Chances are, you'll end up with darker and lighter spots. At the very least, wet sand with 100 or 1200 and then clear-coat. The problem is the cost is probably close to just doing a full repaint. In my humble opinion, these boats are rare and unique enough to deserve a proper paint job.