Isn't that board relatively stiff? I believe people use acrylic with no problems, maybe find some flexible wood and test its resistance to cracking.
Basically, sand to bare wood, primer if you've got it, paint, let it dry fully, clearcoat.
Polyurethane is what I use, but it does yellow your colors a bit. I've heard polycrylic (clear acrylic?) or whatever it's called dries very clear, or if you can find some automotive clear coat. Spray paint works fine, just make sure to test compatibilities among all your ingredients. It would suck to spray on the clear and have it dissolve half your paint.