Here is a fender I modeled in MOI3D as per a tutorial here by Ed Ferguson.




I then import the fender into Blender where I retopo it.




Exported from MOI3D as an obj and imported into Blender. Not the quad/tri count is 14,312. A bit too high for my liking.






I use the commercial plugin Quad Remesher for auto retopo after setting the target quad count. Below is the result with 2531 quads/tris






The only issue I have is with the actual car bodies. I still can not get the hang of it. But for car parts like fenders, wheel rims, I beam or tubular front axles like those used in classic pickup trucks, model As, hot rods and gassers, MOI3D is much better than Blender. I also find MOI3D is much easier and faster to create these parts. I am considering on attempting to model a detailed engine block like a small block Chevy V8, classic Hemi or Flat Head Ford (already created one started in Hexagon3D and finished with Blender but I lacks true scale and dimensions.

I did attempt several times to voxel sculpt a car body in 3D Coat but I find 3D Coat hard to get good dimensions and scale. And 3D Coats auto retopo is hit or miss for me. Blender's Quad Remesher is much easier and I find I get much better results then 3DC auto retopo. I have manually retopo'd in 3DC but find the manual retopo process is much longer and more tedious then modelling the original source object.

Sorry for the late reply KENMO, I don't get notifications on subscribed threads so it's easy to miss replies!
Thanks for sharing your process, yeah quad remesher looks like magic!

And worth the money. I find it much simpler to use and most times, achieves better results then 3DCoat's auto retopo.