I agree that an airbrush is a good investment if you are going to be getting into some serious model-building. Spray cans cost 3x as much as a small bottle of paint, which you can use to paint at least 2 models if you know how to stretch it. I use acrylic paints which clean up with water because I can't be bothered using paint thinner.
I bought a used Pasche airbrush from a friend at work, so I've never used the compressed air-in-a-can ones. But be careful because a cheap airbrush in the hands of an inexperienced airbrusher will yield inexperienced results...
I have a really good hobby store in my neighbourhood which holds classes on many subjects, including airbrushing. If you can find a similar store near you it might be a good idea to sign up once you purchase your airbrush.