There is another way to show flow then tuft testing or windtunnel smoke testing, its nicknamed Fluidviz =fluid visualisation.
They use a parafine based oil, with flourecent pouder in it.
After you did your run you can examen the flow quite good.
The use this in F1 in real training, becouse this gives real world results even though they use the windtunnel 24-7.
At the University TU Delft they also use it.
some examples
Mclaren Mercedes MP4-25 - Forum - F1technical.net
Red Bull RB7 – getting green at Jerez (February test) « Formula 1 tech and art's Blog
Tu delft bobsleigh
http://www.tudelft.nl/live/binaries/.../2006_1_15.pdf
Oil flow visualization
To visualize the surface flow an oil flow visualization technique has been applied. First
petroleum was applied to create a smooth surface. The mixture for the visualization consists
of the following components:
•
Shell Ondina 68 Paraffin; viscosity thick.
• A680 fluorescent oil additive.
After the oil is applied the model is illuminated with ultraviolet light. The oil flow
measurements were done at approximately 60 m/s. For an example see figure 3.13.
Figure 3.13: Example of oil flow visualization