In the past I’ve used Yacht varnish to seal the cut edges. Think paint would do a similar job but I’d be worried that it would be more prone to chipping and flaking. I don’t know though.
If you want to paint it use 2k paint, if you use a roller a normal canister face mask is fine. Put it on thick and sand back and polish any runs. It’ll last an age.
Opinions on how to best protect the ply?
Epoxy sealer? I'd also like to paint it as well..