Hello everyone. Just finished a car model and wanted to share a simple but effective workflow:
While people have demonstrated that it's perfectly possible to make an entire car in MoI, it's tricky to have seamless surfaces when a panel is split into multiple smaller surfaces, and It's hard to make corrections/modifications. A door or a hood are easy to do but panels that run along multiple axes (like a bumper or a rear quarter-panel) require a lot of planning. Where MoI shines is doing a wire mesh of a car body (following blueprints) in no time. What I do is generate this wire, break it up into quad-shaped areas, and use Loft/Sweep/Network to generate quad patches. These are fast to do, easy to edit, but of course they are "unstitched" and produce visible seams. Instead of fighting to get them right I use the whole of this model as an underlying reference in Blender and do re-topology.

First step is splitting the reference image (they usually come with all views in a single image) into multiple images. Now most of them are inaccurate and never lineup. When you crop them into different files their dimensions are always slightly off. So I "decide" that the width & length of the side view and the width of the top view are my "good" dimensions, and then stretch the dimensions of all views accordingly.
Next, I create a box in MoI with the pixel-dimensions of the images and scale it down to a comfortable scale. It's only the proportions we're interested in. When you add the reference images into Moi you use this box to snap and align the images perfectly. The same box can be used in Blender to align the images there too.
I then start to define curves following the blueprints. It's good to use as few points as possible. Two control-points (besides the end-points) are enough in most cases. I Use object snapping to snap curves between them so that they can be trimmed to form quad-areas. At this point we're only interested in the bigger features and avoid modelling the smaller details. After finishing with the curves I generate the aforementioned patches and do an .obj export. In my opinion it's better to export N-gons because it generates mostly quads. You don't need a very high density model, just enough to be relatively curvy. Subdivision modelling in Blender will smoothen things up.
Once inside Blender, I import the model and with it selected, under Object properties->Viewport display, I turn Wireframe to On. I then start by generating a new object for every car panel/part, and again under Object properties->Viewport display, I turn In Front to On. I then turn on snapping and set it to Vertex+Edge+Face. At this point it's just connect-the-dots. The underlying, almost-quad geometry makes this a breeze. You don't need to be very precise, just snap your new quads over the reference, and you can later slide vertices/edges with snapping turned off to straighten edges. The good thing is that MoI generates a very nice flow of polygons and you almost don't have to sweat to decide the count or direction of the loops!

When finished with this it's just a matter of adding edge-loops to tighten specific areas. In my case I then went back to MoI and modeled some parts like the grill, badges, logos, etc. which are way easier to do in MoI, and then imported them to the Blender project. The nice thing about this workflow is you get to use the right tool for the job.
Sorry for the long post and I hope it is useful to someone!