You would score and cut with the good side up. Use a very secure straight edge, a scoring tool and a hook knife. Maybe on concrete.
If the circular saw was working well, maybe you should use it. Just set it up better. Most saws come with a fence. Or clamp a piece of wood to it for a guide like some of the other guys mentioned.
And BTW the table saw method is tough. I had myself and 2 other guys and was surprised I made it. The cut is clean though.