You might try dry ice on them before you do anything else. A local produce delivery truck or the butcher at the local supermarket might have it for free. You can buy it in some supermarkets for about a buck, but I'm not sure how much that gets you. Heat the dent with a hair dryer or do it in the hot summer heat (you're blue car helps as it's a dark color. A little experimentation might need to take place, but I believe you chip off a piece of ice and stick it down into the dent, if you just take a big chunk and sit it on top, I'm not sure it will pull it out. I've heard of body shops doing this to remove hail dents, but I've never seen it done. I have, however, seen the results of it being done. Its also fairly cheap to do, just don't handle it with your bare hands.