put one end of a vacuum cleaner hose in your car's exhaust, and the other end in the crawl space to gas them
OK, I know you are more serious in this post but WTF??? Are you seriously suggesting someone pump car exhaust into their house???
To anyone reading this: DON'T DO THIS!!! YOU MAY DIE!
Just about any kind of fumigation involves filling the house with something poisonous. The trick is, DON'T STICK AROUND while its in the air!
And unlike a lot of poisons that are particulate and coat the walls and ductwork unless you get it off, CO is just a gas that blows away if you leave the windows open.
I'd guess that most people take a vacation while their house is being fumigated. And it works pretty quickly. A weekend excursion would be long enough.
I only suggested it because Josie said she didn't want to hire a pro. I agree with everybody who advised calling somebody who does it for a living.