I want to update this thread with some progress in the hopes that it will solicit some feedback and will inform others of what is possible using relatively easy to use, easy to get software.
I built several models of a car body in Google Sketchup 8. This was possible using the standard tool kit in Sketchup 8 and an plug-in called soapscreen bubble (used for creating a complex "skin" based on lines). All the information I used to build the model is based on YouTube tutorials and lots of time testing and building in Google Sketchup. I personally like Google Sketchup because it's free and there is a ton of information out there on how to use it.
Once we had a detailed model that looked good and other team members liked, we imported the file into AutoCAD 2015. Then we saved the file as a 2010 .DWG file. The conversion from a .SKP file to .DWG looked great! From there, we opened the file using Autodesk Flow Design and began running scenarios. We used a freshly built desktop that has 8gb solid state ram and a 4.4ghz processor, but it still took an extremely long amount of time to get 3D results processed. It appeared that the higher the wind speed the longer it took to get the results and a realistic average CD. 2D results are instantaneous, but only show the air over one plane of the car at a time.
At this point we have not done nearly enough testing to decide on a shape, but have proven that it is possible to build a model in Sketchup 8 and run it in Flow Design. I'll admit, there were several "look at that" and "I have no idea" comments in the first session that we ran it, but we can only learn more from here. Thus far, it has been very fun to build and play with. Now comes the hard work and trying to interpret our results in the most scientific way that we can.
Next steps for us are to test standard shapes (cubes, spheres, airfoils, etc...) and check the Flow Design CD values against industry standards. This will mostly be a sanity check, but if we see a trend we may conduct a correction value analysis. After that we will construct 2 more detailed car models. With the total of 3 detailed models we will make some changes to the shape if we see any obvious areas for improvement. Simultaneously the guys that are contributing the $ to this project are ironing out the details for the final drivetrain dimensions. Then it will be time to conduct analyses with the 3 detailed models we have to include push bars, parachute packs, etc.