Skymedias - Blog Content
A fun way to create a nice white clay render/bake map for it if you're interested...
As mentioned, your methods aren't bad at all it's just that cars simply aren't simple cubes and plain geometry so you will spend a bit of time refining the surface details...some people can take weeks to finish off as perfectly high detailed vehicle for one.
The way I model is by extruding along edges...as I would get the the grip and direction of the mesh flow and don't have to shift edges along too much.
And once you can post a render with wires we can certainly move up from there.
Good Luck