If you are only visualising a car then mesh modelling along with subdivison works just fine. It’s different if you are designing it to actually being physically produced at a factory.
One of my oldest “on the shelf” projects I have is a car model. I haven’t gotten around to complete it because I keep getting ideas for new extensions when I work with SketchUp. (Being a toolmaker and all that…)
I’ve been working from reference photos and outline drawings from a plastic model kit:
Finding “blue prints” help - but beware they aren’t always accurate. The drawings from the plastic kit I used is actually in perspective so the roof looks smaller than what it should be in true orthographic projections. And dimensions aren’t accurate so I found the real physical dimensions detailed somewhere and used them to scale the reference drawings.
(I’m sure Christina is going to find this thread and ask me when the model will be done - it’s been sitting on my shelf for about 10 year. That’s the trouble with hobby projects, so deadlines!)
Recently I obtained Substance Painter and I have been playing with it the last week. Using WrapR to UV map the model, then importing the model into Substance Painter to generate textures to use in V-Ray:
Working with Quads (some tris are ok) simplifies UV unwrapping. I UV mapped the control mesh, then toggled on subdivision. SUbD preserves the UV mapping well from control mesh, especially when it quad based. Then I sent that to Substance Painter.