Underside floor blunder

Hi all,
I ordered my wood for my build. I received it and made a blunder for the ply on the underside of the floor, it’s prefinished with a thick layer of white paint
Can I use a exterior grade paint to finish it (I have a can of pu coat/paint)? Or should I try sanding it off (and epoxy it) or buy a new unfinished ply…
Any ideas are greatly appreciated!
I ordered my wood for my build. I received it and made a blunder for the ply on the underside of the floor, it’s prefinished with a thick layer of white paint

Can I use a exterior grade paint to finish it (I have a can of pu coat/paint)? Or should I try sanding it off (and epoxy it) or buy a new unfinished ply…
Any ideas are greatly appreciated!