Yep, I always use a 6 point socket either SAE or Metric depending on the car. If it is tight, I simply put a length of pipe on the ratchet to get more leverage. I got a new drain plug for my Pontiac at the dealer a while back for about $8. Yeah now just replace it but I think having it done at the dealer might be the best thing. Otherwise pipe wrench but I’d prolly put a vice grip on it with a length of pipe and a hammer. Sometimes though when you are upside down it’s hard to tell which way is off. That’s why a ratchet is nice. You make sure its going the right way to loosen before crawling under.