I love these bartops
About the paint, gloss is tough to pull off on large surfaces.
If you're sanding down anyway, you might want to grab a few cans of that spray body putty. It's like a super thick primer. Sand, spray it on, let dry, sand, repeat, and get progressively down to 600 or 800 grit sandpaper and you can get an awesome finish, even with plywood, or mdf..
Check OND's Astro project for details.