I did a tuft test on our car. Here are a few images from the test.
http://www.flickr.com/photos/6037656...th/2334331320/
You can attach tiny 1/2" sections of thread to your model to simulate a tuft test. I tried it using a shop-vac on a model that i have of our car. It's fun, but pretty much useless compared to an actual test ( based on my testing )
You might try it anyways - it's interesting.
You can also tuft test small areas of your actual car by blowing air towards the section you want to test using a shop-vac. I used the shop-vac on the side glass around my rear view mirror and noticed that the tufts reacted much the same that they did in the actual test.
However, the angle is critical and i knew what i was trying to duplicate after seeing the prior test.