If I had a choice (and free is a good choice) I wouldn't spend any time trying to resurface it as you may make it worse. I would just use a thin piece of tempered masonite (hardboard), and put the smooth side up. It's pretty cheap. When it gets all mucked up, just throw on another sheet. This way you have a solid substrate with a replaceable top.
Or use as a top sheet a thin sheet of melamine or Formica laminated plywood (can be thin, like 1/4"). Glue and finish materials will wipe or scrape off very easy. Also, a cheap fix.
Now, if you're one of the millions of woodworkers who just like cool looking shop items and have to stand back and drool with great degrees of salivation that loads up on the front of your shirt, spend the time handplaning and sanding, and finish off with oil base polyurerthane. Once that is done, don't do any work on it as every nick, scratch and globs of glue will seriously affect your state of mind sending you into hours of depression. :laughing::laughing: