and sanitize the crap out of the spigot area...make sure no bacteria is hiding in there.
Long term, be very careful about scratching the plastic inside the cooler. In a mash tun, it's no big deal, but if you're making a starter in there you really dont want ANY bacteria hiding out in tiny scratches. I think this is why the majority of people use glass flasks that they can directly boil in, easy sanitization of the entire vessel.