If you have saturated the ply, as in the west system, you can use paint with a reasonable expectation of satisfactory result. If you have used fir ply, it might check, sooner or later, even if you had used gel coat.
It may be interesting to note that a good quality house paint will endure as well as some of the high dollar "marine" paints. A good house paint will last ten years and more when applied to your house. It will last plenty long on your boat. It is less expensive, much easier to apply and easier to repair a damaged place. If you use a satin finish, it will not create sun glare as a slick enamel paint would. I am talking about the interior of the boat here.
If you want some non skid places in the boat, then an acrylic house paint is the way to go. Paint the surface and sprinkle some silica sand into the wet paint. Let it dry in place. Vacuum up the excess sand. Paint over the imbedded sand with some more acrylic paint. If you want a less bumpy surface, use pumice powder rather than sand. Pumice will still provide a practical non skid surface but won't hurt as bad if you fall (while battling a huge trophy sized fish) and scrape your elbow or other part of your anatomy. For extreme cases for non skid use Bird gravel. Do not fall into a bird gravel non skid finish.
