Wife was just telling me about some new plastic coating for fabric that ends up like oilcloth. You iron it on. Look for the HGTV web site for some show called High Low show or something like that, in the last couple of weeks.

If you want hard, polyurethane is your friend, paint the board, lay on the cloth, paint the cloth, use a disposable rubber roller to roll out the bubbles, recoat to slick it up. Try a composite construction supply company. I use Aircraft Spruce and Specialty, who cater to homebuilt airplane guys (fascinating free catalog - lotsa neat tools and gauges and stuff - they have or had a store south of ATL).

You'll have to work fast, or find some slow setting polyurethane. You can thin it with mineral spirits to make it saturate the cloth better.